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Title: Old Mines of Southern California - Desert-Mountain-Coastal Areas Including the Calico-Salton - Sea Colorado River Districts and Southern Counties
Author: Mineralogist, California State
Language: English
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OLD MINES
OF
SOUTHERN CALIFORNIA
_Desert-Mountain-Coastal Areas_
_Including the
Calico-Salton Sea Colorado River Districts
and
Southern Counties_
1965
Frontier Book Company
Toyahvale, Texas 79786
_Reprinted From_
_The Report of The State Mineralogist
1893_
_Limited to 1000 copies_
LOS ANGELES COUNTY.
By W. H. Storms, Assistant in the Field.
The mining industry in this county is not as extensive as that of some
of the neighboring counties, but there are mines in Los Angeles County
of unquestioned value, and others which have a prospective value,
dependent to a great extent upon the success achieved in working certain
base ores, which occur in comparative abundance.
THE KELSEY MINE.
One of the most interesting mines in the county is located in the rugged
mountains about 8 miles from the town of Azusa, in the San Gabriel
Cañon. It is commonly known as the Kelsey Mine, and has become famous as
a producer of silver ore of fabulous richness.
The country is made up almost entirely of metamorphic rocks, having
schistose, gneissoid, and massive structure. Both hornblende and mica
occur in these rocks abundantly, the former being frequently altered to
chlorite, or by further change to epidote. Dikes of porphyritic rock
have been intruded into the crystalline schists. In the immediate
vicinity of the Kelsey vein are intrusions of a dark green, much
decomposed, and shattered rock, probably diorite. Faults, great and
small, are numerous throughout the region. Within a few hundred feet of
the mine is a great fault, which may be plainly seen cutting the
mountain. The displacement must reach many hundreds of feet. It has
resulted in bringing in contact on a horizontal plane rocks of entirely
different character. On the south side of the fault the rocks are made
up of quite regularly bedded micaceous sandstones, more or less
schistose, and having a prevailing buff or light gray color. These rocks
dip east at an angle of 20° to 30°. On the north side of the fault the
rocks are harder, of a dark gray color, and containing considerable
hornblende. These rocks are more gneissoid and massive than schistose.
The dip is much less regular than on the south side of the displacement.
Large, lenticular masses of quartzose and feldspathic rock are of
frequent occurrence in the hornblende gneiss, evidently the result of
the segregation of the contained minerals. On the whole there is much
more evidence of the disturbance on the north side of the fault than on
the south side. It is in this area of greatly disturbed strata that the
Kelsey vein has formed.
The vein is of the fissure type and occupies the line of a fault plane,
that at first, perhaps, was a mere crack, but which has become enlarged
by the movement upon themselves of the rock masses forming the walls,
resulting in a grinding and crushing of the rocks by the attrition and
pressure incident to this movement. Into this crevice mineral waters
found their way, carrying in solution the minerals now constituting the
vein.
[Illustration: _FAULTING AND TORSION
OF THE
KELSEY VEIN_]
_The Ore._—The silver occurs as native and as glance (argentite),
possibly partly as chloride and in combinations with sulphur, cobalt,
and arsenic. The associated minerals are cobalt bloom (erythrite), a
hydrous cobalt arsenate, nickel arsenate (annabergite), carbonate and
silicate of copper (chrysocolla), iron oxide, and black oxide of
manganese in a gangue of baryta (heavy spar), with calcite (lime spar)
and some quartz. A clay selvage usually separates the vein material from
the wall, this feature being well developed in places on the foot wall
side, as though open crevices had occurred and the finely divided
material which was carried by the percolating waters had found a resting
place when an open space was reached, the absence of any current
permitting the material to settle.
The clay may have been derived in part from the decomposition of the
overhanging wall, the fine silt settling by gravity on the foot wall
side of the vein. In places a soft, clayey gouge constitutes the entire
vein filling, suggesting that the clay selvage and gouge are also partly
due to the attrition of the walls. Galena occurs sparingly in small
disseminated crystals, but the occurrence is so infrequent as to be
scarcely worth mentioning. In width the crevice varies from a thin seam
to over 4 feet. A banded structure is not uncommon in the vein.
The rocks inclosing the vein differ in various parts of the mine. A much
decomposed rock, containing iron in the form of carbonate, occurs
frequently, while a chloritic, more or less schistose, sometimes
massive, rock, also plays an important part in this connection. The dike
of dark basic rock, resembling diorite, previously referred to, is
exposed at numerous places throughout the workings, often in contact
with the vein, or close to it. Since its formation the Kelsey vein has
been subjected to severe torsion, which has resulted in abrupt fracture
and displacement. To me it seemed very probable that the vein was the
result of chemical precipitation, and no doubt, to some extent, the
replacement of country rock along the line of a fissure or fault plane;
that subsequent to the filling in of the vein the region was subjected
to further violent disturbances, which fractured the rocks along an east
and west course, and causing the turning of a large mass of rock
formation lying south of this fault to the west. The vein being included
in the general movement, was deflected from its natural course north and
south. I came to these conclusions from close observations taken along
the surface of the ground on the course of the vein, and in all
accessible underground workings.
Most of the ore extracted from these workings has been high grade,
usually running over $200 per ton, small lots often assaying several
thousand ounces. The property, at the time of my visit last spring, was
under the management of Dr. Endlich, E.M. This gentleman was making
every effort to systematically open and recover a vein that had been as
systematically and outrageously gouged. The workings were in bad
condition and at some points were positively dangerous. The mine was
gradually assuming an improved appearance and promised to yield better
returns than ever before. A good mill has been erected at the foot of
the mountain, in the San Gabriel Cañon, where a large stream of water
flows during the entire year. An office, boarding house, stables,
corrals, etc., had been built for the accommodation of men and animals.
In addition to this I found a complete assay office and chemical
laboratory, and here Dr. Endlich was experimenting with the rich cobalt
and nickel ores. As a result of his labors in this direction he
exhibited several bars of cobalt speiss containing a very high value in
silver. The assorted ore contains from 7 to 15 per cent in cobalt, 2 to
3 per cent nickel, and from 1,000 to 1,400 ounces silver per ton.
Dr. Endlich thus describes his methods: “The ore is crushed through a
twenty-mesh sieve, mixed with sufficient litharge to produce an 8 per
cent charge, and enough borax is added to take up the gangue (quartz,
heavy spar, carbonate of lime, magnesia, and iron). Carbonate of soda
and flour are mixed with the charge. If the percentage of arsenic in the
ore is sufficiently high to produce speiss none is added; otherwise some
metallic arsenic is mixed in. Some sulphides in the ore and reduced
sulphur from the heavy spar are utilized to produce mattes. The mixture
is melted in large Dixon crucibles; the slag poured off, and the
metallic product allowed to cool. The bars obtained are composed of
lead, silver, cobalt, nickel, arsenic, and sulphur, principally; the
lead being in the form of sulphide, the cobalt and nickel in the form of
arsenides. The bars contained from 4,500 to 7,000 ounces silver per ton.
The slag contained a trace of silver, and averaged about 0.75 per cent
cobalt, which can be worked over by arsenizing, if desired, and the
cobalt obtained in the resulting speiss.”
At this writing about 560 pounds of ore has been treated in this way and
the product shipped to Balbach’s works in Newark, N. J., for refining.
THE VICTORIA MINES.
This property is situated but a short distance from the Kelsey Mine. The
Victoria Mine was operated under English management for an English
syndicate two or three years ago. Lately all operations have been
suspended. The property, whatever it may be worth, is a monument to
mismanagement of the worst sort.
THE LORDSBURG STAMPEDE.
In the month of March, 1892, the report went abroad that rich silver and
gold-bearing rock had been found in the mountains north of Lordsburg, 28
miles east of the city of Los Angeles. So glowing were these stories
that a general stampede for the new mining field ensued. Farmers left
their homes, merchants and clerks in some instances temporarily closed
their stores to join in the rush to Lordsburg. Unfortunately the stories
proved to be unfounded, and, after three weeks of excitement, all had
left the mines excepting a very few, who still had hopes of making a
find.
CEDAR MINING DISTRICT.
Fifty-five miles by rail northeast from Los Angeles, on the line of the
S. P. R. R., is the Cedar Mining District, the principal village being
about the railway station called Acton. In the low hills about Acton,
which rise out of the valley that skirts the northern base of the San
Gabriel range of mountains, are located the gold mines which have been
worked for many years by Mexicans and Americans.
THE RED ROVER.
This is the name of the principal mine in the district. It was located
and worked many years since by Mexicans, but has during the past eight
or ten years been in the hands of Americans. The vein strikes northwest
and southeast, dipping to the southwest at an angle of 50° from the
horizon. The rock is a white, fine-grained, saccharoidal quartz, showing
in places bluish bands. It contains free gold in variable amount, with
some iron sulphuret. A very large amount of quartz has been stoped from
the vein and crushed in various mills.
The Red Rover is quite extensively developed, the new vertical shaft
being down over 400 feet. The old inclined shaft, which is sunk on the
vein, is down 220 feet. Several levels are run out from both these
shafts, which are 200 feet apart. The new shaft was sunk between the
main vein and a spur which branches from it. A crosscut was run out
toward the spur, which is opened on the surface, but it was found it did
not go down. A crosscut was then run toward the main vein, which was
found intact, and a drift was carried in 60 feet on the vein.
The country rock is mostly massive metamorphic, very much broken and
faulted. Nearly every mine in the district has been displaced more or
less by these faults. For some reason the Red Rover has been shut down
for some months past. It is understood that operations are to be
resumed.
THE NEW YORK MINE
Is situated within half a mile of the Red Rover, and is similar in
character. The quartz is said to mill $10 to $25 per ton. The owner has
a five-stamp mill, which is complete and does good work. The vein is
from 1 to 3 feet in width. It has produced considerable bullion.
Other mines of the vicinity are the Topeka, Union, Escondido, King of
the West, and Santa Clara, each of which has seen better days. The first
three mentioned have been large producers, but are worked down to the
water line, and a base ore proposition now faces the owners in the form
of iron pyrites.
IN THE MAIN RANGE.
Up in the main range of the San Gabriel Mountains, on the north slopes
of this rugged chain, are located a number of veins, on which
considerable work has been done. The veins are well defined, ranging
from 1 to 4 feet in width, striking northwest and southeast, and dipping
uniformly to the northeast at a high angle. All of these veins contain
gold, but all quickly run into sulphurets. All the mines are idle at
present, but something brighter is hoped for. The sulphurets are said to
contain sufficient gold to make chlorination profitable. If this is
actually the case there is an abundance of material to work upon.
LIPARITES AND TUFAS
In the region about Acton are many hills of liparite (quartz-bearing
trachyte) and tufa, which are identical with the rhyolites of the Calico
region—the same violet-brown, porphyritic liparite; the same pea-green
and buff-colored tufas; the same conglomerate; in fact, an exact
facsimile of the Calico range. There are no great beds of sedimentary
rock, however, and these liparite hills are comparatively small,
isolated masses. As far as my knowledge goes ores of silver have never
been found in these rocks in the Acton district. Careful prospecting may
possibly discover such ores.
PROSPECTS OF THE CAMP.
Owing to the fact that the gold mines of this district have been worked
to the water line, almost without exception, what now remains to be done
to perpetuate the prosperity of the district, is to concentrate the
sulphurets, working them by chlorination in works built in the district.
Wood and water are both obtainable at moderate cost, and the
sulphuretted ores of this district that contain but a very few dollars
per ton should pay. The cost of mining, transportation, crushing, and
concentrating should not exceed, ordinarily, $5 per ton of quartz, and
the expense of treating the concentrates should be under $10 per ton.
Base ores containing $10 per ton as it comes from the vein should
realize a profit in this district, and I am told that many of the mines
produce rock of a much better grade than that mentioned.
SAN DIEGO COUNTY; ALSO ORANGE AND SAN BERNARDINO COUNTIES.
By Harold W. Fairbanks, F.G.S.A.
The topography of this region has been quite thoroughly described by W.
A. Goodyear, in former reports of the State Mining Bureau. The structure
of San Diego County is comparatively simple. Three main divisions might
be made: the desert on the east, the Peninsula range of crystalline
rocks in the middle, and the nearly level mesa on the west. The
Peninsula range is supposed to represent the southern continuation of
the Sierra Nevadas, but in just what relation it stands to the Sierras
has been a matter of dispute. The Peninsula range in San Diego County
forms one main mountain chain. It maintains this simplicity of structure
southward, forming the backbone of the peninsula of Lower California.
Northward it becomes broader and more complex, rising in the lofty San
Jacinto and San Bernardino ranges on the east, and the Santa Ana range
on the west, while the region between is filled with mountains and
valleys irregularly disposed.
Complex as is the topography of this region, the geological problems,
though often difficult to solve, are quite simple. The higher mountains
are formed wholly of ancient crystalline schists and massive rocks,
respecting the age of which a great diversity of opinion has existed;
while the region bordering the coast consists of unaltered Cretaceous,
Tertiary, and Quaternary deposits.
Owing to the very limited time given me to prepare my field notes for
the press, they will be given substantially as they were taken in the
field, without any attempt at systematic arrangement.
The crystalline rocks of San Diego County are varied in character, and
of much interest. No opportunity has been given me to study the large
collection made, and the determinations given are simply the result of
superficial examination, and are subject to correction.
The bay of San Diego is bordered on the east by gently sloping mesas of
modern Tertiary and Quaternary age. These unaltered strata are
characteristic of the western slope of the Peninsula range through its
whole extent. They sometimes rise as high as 3,000 feet; though in San
Diego County they do not exceed 1,500 feet. The upper portion of these
beds consists to a great extent of coarse, loosely cemented
conglomerates. The rivers issue from the higher mountains through narrow
valleys or cañons, and have cut valleys, often quite broad and with very
steep sides, through the mesas to the ocean.
The Otay mesa has a height of about 500 feet, the western portion being
somewhat higher than the eastern, indicating a recent elevation near the
coast. The soil of the mesa is adobe, due to the decay of porphyry
mountains to the east. Under the adobe there is a calcareous marl, often
many feet thick.
The first exposure of the older rock seen as one goes up the Otay River,
is in a hill rising through the mesa about in the center of the grant.
It is a part of the extensive porphyry intrusives, which, in southern
San Diego County, form a number of high mountains between the granite
and the mesa. To this formation belong the San Miguel and Otay peaks.
This exposure on the Otay River is a felsitic breccia. It contains a
felsite base (intimate mixture of quartz and feldspar), in which are
imbedded fragments of felsite and chlorite. No more rocks appear for
about 2 miles up the river. Then we reach the base of the long ridges
which lead up to the Otay Peak. Some interesting rocks are exposed where
the stream issues from the cañon. The greater portion are fine dark to
greenish aphanitic rocks, with green chloritic or epidotic nodules.
Bunches and dikes of coarse to fine grained porphyritic rocks
occasionally appear. They probably belong to the diorite porphyrites.
The rock continues very much the same for several miles farther east; at
times it is almost wholly feldspar. In the cañon above El Nido Post
Office it changes to a light green feldspar porphyry. Near the western
edge of the Jamul grant a dark-colored porphyry takes its place, and a
little farther east it becomes jet black, with small white feldspar
crystals, producing a very pretty effect.
The mesa conglomerates extend along the top of the low hills bordering
the valley nearly to the eastern edge of the Jamul grant. A great
variety of rocks appear along the Campo road between the Jamul grant and
Sheckler’s, on the Cottonwood. Near the eastern end of the grant the
porphyry is followed by fine-grained granitic rock, frequently becoming
schistose. Numerous dikes and bunches of dark diorite cut through this
rock. As Dulzura Post Office is approached, these rocks change to mica
and hornblende schists, and are filled with intruded dikes of diorite
porphyrites. Bodies of massive syenite and coarse granite were also
seen. About Dulzura many of the dikes have the appearance of diabase.
Between Dulzura and Sheckler’s the country rock is largely micaceous and
chloritic schists. Massive granite forms the high, rugged mountains
east, extending in an arm westerly across the road. The schists have a
northwest strike, vertical dip, and are evidently of metamorphic origin.
They form a strip of country extending in the line of strike from near
Sheckler’s to the Sweetwater River, and are situated between the wide
belt of porphyry on the west and the coarse intrusive granites on the
east, which rise to form Lyon’s Peak and other rugged mountains.
The first rock met east of Sheckler’s, on the Campo road, is coarse
hornblendic granite, so decomposed that a fresh specimen could not be
obtained. Dikes of fine-grained granite intersect it in every direction.
Three miles west of Potrero, mountains of olivinitic diabase rise on the
north side of the road. This rock is very similar to many large bodies
of intrusives through the mountains between Julian and the Tia Juana
River. It has evidently been intruded into the granite, for dikes extend
out, intersecting the latter rock.
Potrero is located in a valley of several hundred acres in extent, and
surrounded by granite mountains. It has an elevation of 2,400 feet.
South of Potrero, along the boundary line, the mountains show large
areas of the dark dioritic and diabasic rocks. The hills immediately
south of the valley consist of hornblendic gneiss; strike east and west.
Eastward, toward Campo, the rock is chiefly a coarse white granite, very
easily decomposed. It shows a slightly gneissoid structure for a number
of miles. It does not seem to represent the bedding of a sedimentary
rock, but of parallelism of the constituents, induced in the magma by
movement or pressure. Long, drawn out, lenticular inclusions are often
present, and are arranged parallel to the schistose structure. These
consist largely of hornblende, with little feldspar.
In the vicinity of Campo the topography of the country changes from that
of high mountains and deep, narrow valleys, to an elevated mountain
plateau with meadows and rounded granite ridges. The mountains are
covered with brush, while live oaks are numerous in the valleys. The
country maintains these features while gradually rising to the divide 8
miles east of Campo. The granite is so deeply decomposed along the
summit region that no good samples could be obtained. Campo has an
elevation of 2,600 feet. The bare, rounded ridges closely resemble those
left by glacial action, but their slope is produced simply by the
cleaving off successively of the more angular portions in great slabs.
Many fine examples of this manner of decay appear about Campo. The
corners are decomposed faster than the smooth surfaces, and thus finally
a shelly concentric structure results. The fresh massive central portion
weathers out like water-worn bowlders. The presence of rugged angular
ridges results either from a less inherent tendency to decay, or to a
comparative freedom from crushing. Four miles northeast of Campo is an
outcrop of coarse hornblendic granite, with large six-sided mica scales
and numerous yellow crystals of titanite. The height of the divide is
3,800 feet. Near the summit the rocky ridges all disappear and the
country becomes covered with granitic sand. Erosion here is evidently
very slight. The country descends gradually on the east to Jacumba
Valley, being sandy for some distance. This finally gives place to bare,
rocky ridges and cañons. Veins of fine granite, and others of feldspar
and quartz, are abundant on the eastern slope.
Before reaching Jacumba Valley a body of mica and hornblende schist is
encountered. The schists do not form a regularly defined belt, but often
appear as inclusions in the granite. These inclusions have a very
variable strike, and from their relation to the granite it is evident
that the latter is intrusive.
Jacumba Valley empties northward into the desert through a narrow gorge.
It has an elevation of 2,600 feet, the same as that of Campo. It is
several square miles in extent, the greater part of which is in Lower
California. The warm springs here are considered quite medicinal. The
schists just described occupy a large area west and north of the cañon
through which the valley empties. They are cut in every direction by
dikes of granite and others, consisting of a very coarse aggregate of
quartz and feldspar with a little muscovite mica. A high mountain
several miles north of the valley is distinctly ribbed all over by them.
The schists extend northward toward those which outcrop on the eastern
slope of the Laguna Mountains and at Julian, but are cut off by a body
of intrusive granite. They undoubtedly belong to the same series.
Gold-bearing veins have been found in them a little north of Jacumba
Valley.
At the north end of Jacumba Valley, and on the west side of the outlet,
is an area of volcanic rock, probably basalt. It forms a table-land,
gently sloping toward the valley, and rising 600 or 700 feet at its
northern end. It is underlaid by gravels and conglomerates. Just east of
this is a black butte, rising perfectly symmetrical to the same height.
It consists of bedded lavas, with tufa at the bottom. In spite of the
fact that it is shaped like a crater, its structure is different, and it
is probably a remnant of the flow which once covered the outlet to the
valley.
The high range of mountains between Jacumba Valley and the desert has an
altitude of something over 4,000 feet, but where the road crosses it, it
is only 3,100 feet. Basalt outcrops also on the eastern side of the
valley. North of the road to Mountain Springs it forms a series of
plateaus, the highest of which reaches a height of 3,900 feet. It forms
the summit of the range, being 800 feet above the granite forming the
pass. South of the pass several miles the granite rises much higher and
the lava lies along its western slope, extending an unknown distance
below the line.
Large deposits of water-worn bowlders and gravels lie along the eastern
slope of Jacumba Valley. Among them are pebbles of porphyries, black
quartz, and others not seen in place in this part of the county. A short
distance west of the summit they are found in beds with gravel and
sandstone, dipping southwest. These late Tertiary deposits are overlaid
by the volcanic beds. The volcanic plateau which rises so high north of
the pass has a thickness of 500 to 600 feet. Massive and bedded lavas
form the upper half of this thickness, the lower portion consisting of a
volcanic breccia. The beds lie nearly horizontal. On the west are two
lower terraces, also capped with lava and abutting against the higher.
The whole is underlaid by sand rock of granitic origin. It is nearly
level in places, in others it dips to the southwest. It is very strange
that these lava beds, with nearly level flowage lines, should be found
at such greatly varying elevations about Jacumba Valley, and be
underlaid everywhere by such similar tuffs and sandstones. My
investigations disclosed no volcanic vent, and it is possible that the
lava issued from fissures, as was noticed elsewhere in the county.
Another interesting question is the origin of the sandstones and
conglomerates. The sandstone underneath the high plateau is higher than
the divide at that spot, and the only granite within miles that exceeds
it in height, is the narrow ridge which rises on the southeast. The
erosion must have been very great along the ridges since the sandstones
were deposited, but the valley cannot have changed much. There may have
been great elevation along the crest of the range bordering the desert
since the deposition of sandstone, tilting up the sandstone and lava on
the eastern slope, but elevating without great disturbance those near
the summit. Southeast of Mountain Springs is a body of bedded tufas
reaching an elevation of 2,300 feet, and dipping to the east away from
the range at a considerable angle.
The presence of these modern sandstones at so great an elevation nearly
on the crest of the Peninsula range is a very interesting fact. Either
Jacumba Valley was a lake, or a great elevation has taken place in
comparatively recent times, raising the valley from the sea-level.
Appearances indicate that during late Tertiary times this range was
almost submerged beneath the sea.
The rocks between the summit and Mountain Springs are chiefly gneissoid,
at times granitic. They contain bodies of fine dark mica schist, and
many dikes of very coarse muscovite granite. The descent to the desert
is very abrupt over bare granite ridges. Mountain Springs, an old stage
station, is located on the side of the mountain at an elevation of 2,300
feet. From the springs the road descends along the dry bed of an arroyo
to the desert. The most of the distance is through a rocky cañon, where
there is an excellent opportunity to study the relations of the gneiss
and granite. For some distance down from the springs the rocks continue
to be gneissoid, but through the lower end of the cañon they become more
massive and coarse, and all the veins characteristic of the gneisses of
the higher mountain region disappear. At the upper end of the cañon is a
dike of very coarse granite, with large biotite crystals instead of
muscovite. This is the only instance in which biotite was seen in one of
these coarse dikes. Banded gneiss, varying from very thin to very thick
bedded, alternate with other rocks, to all appearances massive granites,
but in surface decay the latter break up into slabs of varying
thickness, parallel to the schistose structure of the gneisses. The
banding is caused by an excess of mica or hornblende, chiefly the
latter, arranged in parallel layers. These strata are often very thin,
varying from one fourth to one half inch and upwards in thickness. They
are very regular, but often discontinuous; stop, and in course of a few
feet begin again. These features are generally supposed to indicate
metamorphic origin, but at one spot a body of dark mica schist is cut by
a dike a foot wide or more of this dark banded gneissose rock. This dike
cuts across the stratification of the mica schist, showing conclusively
the intrusive nature of at least a part of these gneisses; and it is
quite possible that the inclusions of mica schist are the only really
sedimentary rocks present. In places the rocks which show this banding
have the constituents arranged in the bands independent of any
direction. At one spot a distinct, well-defined mass of mica schist, 15
feet across, is imbedded in a granitic rock. At one side this gneissoid
structure extends through the inclosing rock and abuts sharply against
the mica schist. The banding shows no constant direction; in the cañon
it is northeast. The bands sometimes become wavy.
As the cañon opens out to the desert, hills appear on either side formed
of volcanic tuffs. They dip northeast 30°. Underneath is a sandstone
wholly unconsolidated and dipping in the same direction 40°. This
contains no lava pebbles. The fragments of the tuff are quite varied in
character and generally quite angular. They are imbedded in a volcanic
mud, free from granitic detritus. In some of the strata appear thin beds
of lava, seeming to represent a flow. These tufa hills extend
northwesterly along the base of the granite mountains for 10 miles or
more. It is not known how far they go in a southerly direction. In
places they form mountains of considerable size high up on the side of
the range. The range of mountains between this point and Carrizo Creek
appears also to have some volcanic beds on its southern slope. The open
desert at the foot of the mountains has an elevation of 1,200 feet. It
slopes gently for miles in an easterly direction and consists largely of
loose sand.
Between Mountain Springs and the summit is another illustration of the
fact that lamination in a crystalline rock is no proof of its
sedimentary origin. A small dike less than 2 inches thick cuts across a
coarse biotite gneiss at an angle of 30°. It is separated from the
gneiss by a thin layer of quartz and feldspar. It is made up of the same
constituents as the gneiss, arranged so as to show a well-pronounced
gneissoid structure. This is very similar to the large dikes seen in the
cañon.
The road was followed back to Campo, and from there the Laguna Mountains
were climbed. The road ascends a long, narrow cañon on the southern
slope. At the entrance to the cañon, 4 miles southeast of Buckman’s
Springs, the mountains are high and rocky, being formed of thin-bedded
gneisses, which, in many places, blend into mica schists. They strike
parallel to the mountain axis, a little west of north; dip 70°
northeast. Three miles up the cañon the gneiss becomes thick-bedded and
is finally replaced by mica diorite, which forms the hills on both
sides. Granitic dikes outcrop near the junction and sometimes apparently
in the diorite. There is often a blending between the two, as if the
intrusion of both took place nearly at the same time. The region east of
the southern end of the mountains is formed of coarse granite,
decomposed to a considerable depth. The mica diorite extends northward,
forming the whole central and western part of the mountains. On the east
it is bordered by a slightly higher ridge, forming the crest of the
mountains. This rock does not decompose as easily as the granite and
gneisses on the west, and there consequently remains a mountain plateau
having an elevation of about 5,500 feet. There is a considerable amount
of pine timber and open meadows. The dark diorite forms one of the
highest peaks of the Laguna Mountains, rising 6,250 feet. The highest
portion of the mountains lies to the northeast, and is formed chiefly of
a quartzose mica schist. From the eastern crest of the range a most
magnificent view of the desert is obtained. The strata on the crest
strike north 15° west, dip 70° northeast. The descent of 4,000 feet to
Vallecitos is very abrupt. Near the crest it is almost as steep as the
dip of the rocks. The mica schists in places approach gneiss in
composition, but all of this series of rocks forming the crest and
eastern slope very probably belong to the Metamorphic Series. South of
this point the Laguna Mountains do not terminate so abruptly, but extend
out in long, gradually descending ridges for many miles. The mica
diorite extends north of the Laguna about a mile, when the schists on
both east and west sides unite and extend north toward Banner. They are
intruded by granite and diorite in many places. The body of diorite
forming the Laguna plateau is about 8 miles long and 1½ to 2 miles wide.
The highest peak is not over 200 feet lower than the Cuyamaca, rising
6,300 feet. The diorite seems to have been intruded in the middle of a
considerable area of mica schists, for this rock outcrops on all sides.
On the west, toward Pine Valley, they carry the gold veins of the Pine
Valley district. The descent is very abrupt to Pine Valley and Buckman’s
Springs. The schists and gneisses extend about 3 miles south of the main
portion of the mountains, when they are replaced by coarse hornblendic
granite.
Buckman’s Springs has an elevation of 3,400 feet. Here are some very
excellent soda springs, the only ones I know of in this section of the
State. A coarse, dark diabase outcrops in the edge of the mountains just
north of Buckman’s and also a little farther south, on the west side of
the valley.
A narrow cañon leads up to the divide which separates the valley of the
upper Cottonwood from Pine Valley. The western prolongation of the
diorite of the Laguna Mountains appears near the road on the divide. The
prevailing rock is, however, of a granitoid nature and filled with many
large bunches of massive white quartz. Pine Valley has an elevation of
3,800 feet. Gneisses and hornblendic and micaceous schists outcrop
between the valley and the divide east of Descanso. The strike is north
and south. One mile southeast of Descanso there is another outcrop of
the coarse diabase or gabbro which forms so much of the Cuyamaca peaks.
Descanso has an elevation of 3,400 feet. The rock which outcrops for a
number of miles along the road to Stonewall is a coarse, easily
decomposed granite, rising in rounded knobs over a rolling,
brush-covered country.
The Pine Valley district lies in a belt of gneissose, mica schist, and
quartzose rocks, which extend in a direction a little west of north.
They begin about 2 miles south of Pine Creek and extend, probably
unbroken, through to Banner and Julian. It is 4 miles north to the Deer
Park district. The metamorphic schists widen as this district is
approached. They extend from the desert slope to Deer Park, where a body
of diorite has been intruded, and from there westward 2 miles to the
Cuyamaca grant. A half mile west of the camp the slaty mica schists and
quartzites are well defined. A vein of gold-bearing quartz has been
traced for several miles in these rocks, and a number of locations have
been made on it. The strike is north and south, dip 80° to the east. A
body of white crystalline limestone lies in this formation, about 1½
miles southwest of Deer Park. The body of micaceous diorite which
extends through this camp is about a mile long, and is quite gneissoid
in places. Near its southern end it incloses narrow bands of hornblendic
and feldspathic rock, containing garnets. The veins are numerous in this
diorite, and extend in every conceivable direction. The diorite has been
greatly crushed at some time, with fissures in every direction; hence,
the irregularity of the quartz veins. The veins are generally bunchy,
and not often very large. They seem simply to follow the exceedingly
irregular fracturing of the diorite, which is decomposed to a
considerable depth. The work thus far in this district has been confined
to the surface, so that nothing can be said in regard to the permanency
of the veins. The elevation of the camp is 4,600 feet.
Two miles northward an outcrop of coarse biotite muscovite granite was
met. It is about 2 miles long and 1 mile wide, having schists on all
sides of it. This is the only example of typical granite (according to
Rosenbusch) that was seen in Southern California. A broad valley,
occupied by Mr. Harper’s ranch, has been eroded in the center of this
granitic mass.
Northward, along the crest of the range overlooking the desert, mica
slates appear. They are so little metamorphosed as to closely resemble
argillaceous slate. They strike a little west of north, dip 70° to 80°
east, and maintain the same character north to Banner and Julian.
The road from Julian to Stonewall crosses mica schist and gneisses for
about half the distance. Then we met outcrops of a dark basic rock,
ranging from fine to very coarse texture. It extends southward and
covers a large extent of country. The three Cuyamaca peaks, the highest
in the southern part of the county, are formed of this rock. This rock
was again met about half a mile west of the Stonewall Mine. It extends
westward across the mountains for at least 2 miles, and some miles south
of the main peak. In places it has a schistose structure. Near the
outlet of the Cuyamaca reservoirs it is filled with vein-like aggregates
of coarse hornblende crystals, which are probably the result of
secondary crystallization in fissures or cracks of the almost
consolidated magma.
The formation in the vicinity of the Stonewall Mine is biotite gneiss.
Toward the east it is not sharply defined from the mica schists. On the
west it is generally more granitoid, though at one spot near the lake
there are finely laminated schists, dipping 70° southwest. Southward,
also, the gneisses become more massive and coarse. At the northeastern
base of the main peak a body of coarse granite is partly inclosed in the
norite. This norite assumes a dioritic habitus near the granite, with
the development of biotite mica.
The valley of the Cottonwood was followed down several miles, when it
was left and the Morena Valley traversed to its head. The mountains
south of the valley are formed of a dark syenite. North and northwest
the higher mountains consist of granite, with a great development of
mica and hornblende schists along the slope facing the valley. Many
granite dikes have been intruded into the schists. North of Mr.
Candler’s there is a great dike of pegmatite, carrying small garnets,
tourmaline, mica, and large masses of quartz. This pegmatite dike cuts
across the cañon, forming a precipice on its lower side. On the upper
side the soil has been retained, forming a small but fertile valley. The
strike of the mica schists on the north is quite unusual, being north
75° west, dip nearly vertical. Dark syenite lies on the west of this
little valley. Morena Valley has an elevation of 3,400 feet. A rough
road leads over the mountains west to McClain’s ranch, a distance of 10
miles; the highest point reached having an elevation of 4,000 feet. Near
the summit there outcrops a body of coarse eruptive rock, probably a
diorite. It consists of coarse hornblendic aggregates in a light-colored
feldspathic matrix. This is followed by syenite, and that by coarse
white granite as far as McClain’s. The granite about the valley is
coarse, with dark, fine crystalline inclusions. It has every character
of a truly eruptive rock, even to the minute spaces between the
components, left at the time of crystallization. The road now descends
to a branch of the Cottonwood, and from the creek there is a long,
gradual ascent to the pass north of Lyon’s Peak. The north side of the
pass is formed of another high and rugged granite range. This section is
one of the wildest to be found in San Diego County. The mountains are
bare granite, often precipitous; the valleys small and covered with
brush. Crystalline limestone is reported to have been found in the
granite 5 or 6 miles northeast of Renney’s Pass. A very interesting
eruptive rock outcrops east of the pass, on the north side of the road.
In places it resembles the norite from Cuyamaca peaks. The rock consists
largely of large, dark, cleavable crystals filled with small granular
crystals of a green color, probably olivine. A large portion of the dark
crystals are undoubtedly pyroxene, though there are some showing
hornblende cleavage. This is one of the most peculiar and interesting
rocks seen in the county, but, from lack of any opportunity to make a
microscopic examination, no more definite definition can be given.
Coarse granite extends some distance west of the pass. It is decomposed
to such a depth that no specimens could be obtained. A mile west of the
pass a fine granite, apparently metamorphic, replaces the other. It
contains much quartz, little mica, and yellowish feldspar. Some distance
down the new grade a large body of diorite outcrops. It is one of the
southern arms of a great mass of coarse, dark rock which forms the high
mountains about Dehesa Post Office, on the Sweetwater. A large portion
of this rock very closely resembles that forming the Cuyamaca, and is
probably a gabbro.
Near the foot of the grade, 2 miles east of Jamul Post Office, this rock
is very coarse, with large hornblende crystals. It extends out in the
form of arms or dikes into the adjoining granitic rocks. This rock is
very tough and heavy. Gneiss outcrops for 2 miles westward. It varies
between thin-bedded micaceous strata and thick-bedded, almost granitic
forms. It strikes north 15° east, dips 70° to 80° east. Farther down,
toward the Oakdale House, this is replaced by coarse eruptive granites.
Just below the Oakdale House there is a very interesting contact between
granite, quartz porphyry, and diabase. The first rock exposed below the
house is a rather dark micaceous syenite. Beyond this the rock becomes
coarser, containing large grains of quartz and glassy feldspar, with
inclusions of a very dark diabasic rock. In a little cañon which comes
down to the road from the east, this rock comes into contact with one
which varies from a feldspathic mica schist, through a gneiss, to a
quartz porphyry. The junction is very irregular and the two rocks are
slightly mixed; sometimes branches of the syenite are partly inclosed in
the porphyry. Some portions of the syenite show gas pores, or spaces
left at the time of consolidation, one fourth to one half an inch in
diameter. They are partly filled with secondary quartz. The next rock
exposed up the cañon is a mica schist; strike 15° west, dip vertical.
Quartz porphyry follows this, then an irregular dike of granite, in
which are imbedded nodules of quartz porphyry, some nearly a foot in
diameter. Above the granite there appears a granitoid gneiss, with many
cavities, arranged with their longer axes parallel to the schistose
structure. This changes into a coarse, knotty granite, containing large
nodules of dark petrosilex. A slight blending is noticeable. Farther up
this is succeeded by a micaceous quartz feldspar porphyry, showing a
somewhat gneissoid structure. It is out at right angles to this
structure by jointing planes lying thickly together. It has a milky,
vitreous luster, and contains inclusions of very coarse granite. The
next rock exposed is a diabase 200 feet across. It is coarse in the
middle and aphanitic on the edges. Adjoining it are bunches of granite
and a fine, dark, compact mica schist, showing traces of little pebbles
in places. The schist changes to a petrosilex, which comes in contact
with a dike of very coarse granite. At the upper edge of this granite
outcrop, and inclosed in it, is a stratum of fine, dark mica schist and
a dike of quartz porphyry. At one end these inclusions are hidden, but
at the other they have been bent, fractured, and the pieces separated
some distance in the granite. (Fig. 9). This is a most interesting
example of the intrusive nature of the granite.
[Illustration: Fig. 9.]
[Illustration: Fig. 10.]
The granite dike is bounded on its upper side by one of aphanitic
diabase 2 feet wide, followed by granite again. Nodules of the diabase
appear in the edge of the granite. A stratum of wavy quartzose gneiss 10
feet wide follows the last dike of granite. It changes across the strike
into a coarser gneiss, and that into irregular and partially blended
masses of coarse granite, filled with long fragments of porphyry similar
to a dike on the east. (Fig. 10.) The quartz porphyry is very compact
and brittle, and has a conchoidal fracture. The porphyry dike has a
width of 8 feet. About it is still another dike of granite 12 feet
across, and containing many long fragments of a diabasic rock, which
appears next in the succession.
The diabase is cut by small, interlacing granite seams for 6 or 8 feet,
and also contains some large, irregular, lenticular masses of the same
rock. Still farther is another dark dike cut squarely across by granite.
Fine granite and quartz porphyry dikes occur still farther east. The
porphyry dikes all run about north 35° west, average dip 70° southwest.
They extend along the summit of a ridge for more than half a mile, when
the coarse granite becomes the country rock. On the summit of the hill
at the head of the cañon are strata of metamorphic rock, and also some
veins of pegmatite, cutting across the porphyry. This wonderfully varied
succession of rocks does not cover a width of more than a quarter of a
mile. The relations exhibited here prove that the porphyry and diabase,
as well as the schists, are older than the granite. The strip of country
between the ancient porphyries of San Miguel and the coarse granite of
Lyon’s Peak and the ranges north is remarkably rich in its variety of
intrusive rocks.
On the north bank of the Sweetwater, just above where the Spring Valley
road crosses, is a large exposure of coarse granite, containing so many
inclosures of a dark dioritic rock as to present the appearance of a
conglomerate. It is cut by bunches and ramifying dikes of fine granite
and diorite.
At Dehesa the granite is replaced by norite, which forms a high mountain
on the north side of the river, and extends southeasterly 3 or 4 miles,
forming two high peaks. In this are veins of hornblende aggregates, and
in general appearance the rock bears the closest resemblance to that on
the Cuyamaca.
The crystalline rocks exposed between the Sweetwater and El Cajon Valley
generally show more of a dioritic composition than granitic. They have a
glassy feldspar, much hornblende, and little quartz. There are two
varieties: one is light colored, and forms most of the country; the
other is darker, occurring in bunches and dikes. Southwest of the valley
the rocks are more granitic. On the road to Spring Valley they give
place to a hard, light—colored felsitic rock, containing specks of
chloritic matter. Masses of granite appear in places, intruded into the
rock. As it decays it becomes jointed, and seems to be reduced mostly to
kaolin. Near the railroad, northwest of Spring Valley, rocks outcrop
which belong to the series of dark intrusives, tuffs, and porphyries so
extensively developed west of the granite. The rock here has a
fragmental appearance in weathered specimens. It has a dark green color,
and is of uncertain composition. The most western exposure of this rock,
before it becomes covered by the mesa, has much the same character. It
is without doubt an ancient intrusive, very greatly altered. It contains
bunchy dikes of white feldspathic composition, which easily reduce to
kaolin. The whole exposed width of these rocks west of the granite at
this point is over a mile, about half of which is tufaceous. By
tufaceous is not necessarily meant a fragmental intrusive deposited in
water, but for lack of any other term it is used to designate those
fragmental intrusives of plutonic origin which are so abundant in
California.
Between the Oakdale House and the Sweetwater River, on the road to the
dam, dark quartz mica diorites outcrop. They have been intruded by
coarse granite in veins and bunches. A body of dark aphanitic rock, of
uncertain origin, is inclosed in the diorite near the river. It may be a
portion of the aphanitic rocks associated with the porphyries farther
west. A little distance down the river the diorite is succeeded by
conglomerate rocks, containing small garnets. The fragments are
feldspathic in composition. Dark feldspathic porphyry then forms the
prevailing rock for some distance. It shows great variations. Much of it
contains no distinct crystals of feldspar, but is mottled by light green
felsitic bodies of irregular outline. These contain chloritic
substances, which decay out, leaving holes. There is a great variety of
these ancient intrusives exposed along the sides of the river north of
San Miguel Peak. None of the other crystalline rocks in San Diego County
appear so old or show so much alteration.
Farther down the cañon the rock assumes a fragmental appearance, having
masses of feldspar in a dark matrix. It finally becomes a pronounced
breccia, being formed largely of angular, felsitic fragments. The base
in which these fragments lie decays away and leaves them standing out on
the surface. This may be a tuff formed in water, but the matrix has
undergone such alterations that nothing certain can be said about it.
This breccia continues to the lower end of the cañon. An interesting,
light-colored dike was observed here. It is so filled with minute
spherical amygdules as to resemble in structure an oolitic limestone.
The breccia continues as far as the Sweetwater Dam, where it is replaced
by feldspar porphyry. The porphyry shows much variation; in places no
feldspar crystals are present, chlorite taking their place. These rocks
disappear a quarter of a mile west of the dam, and mesa-like hills
extend down to Chula Vista. These consist of soft sandstones and some
calcareous deposits. Dark rocks, belonging to the series just described,
outcrop near the mesa road from San Diego to El Cajon. It forms a long
ridge south of La Mesa. The rocks are in part tufaceous, and in part
dark green and massive, with felsitic inclusions. Near the Eleven-Mile
House the granite is filled with dark, bowlder-like inclusions.
Hornblende is an important constituent of the granite. It is more than
likely that many of these so-called granites are really diorites. The
mesa formation terminates in an abrupt escarpment on the west of Cajon
Valley. The valley comprises many thousand acres of very fertile land.
Granitic knobs rise in many parts of the valley, showing that the
alluvium deposit is underlaid by it at no great depth. North of the
valley, for a number of miles, the crystalline rocks are covered by the
mesa conglomerates. Granitic rocks are the only ones exposed for many
miles east of Lakeside. Just above Forster’s there is a small outcrop of
gneiss and mica schist; strike north 35° west, dip 70° northeast. The
rock exposed along the grade is a coarse biotite granite, with much
quartz and glassy feldspar. A dike of quartz porphyry varying to granite
porphyry outcrops by the road at the top of the grade. This does not
seem to be sharply defined from the adjoining granite. A dark hornblende
granite or diorite begins here and outcrops along the road for several
miles toward Ramona. Three miles from the town there appears a dark rock
with a somewhat resinous luster. It is probably a diabase. The Santa
Maria is a large, plateau-like valley, with low granite hills
surrounding it. Light-colored granite, becoming somewhat hornblendic,
extends some distance east of Ramona, when it is replaced by a dark
diorite. The latter extends along the road for 2 miles. It has glassy
feldspar, and in places much mica. Four miles west of Ballena the
granite is filled with pegmatitic veins, running in a northwesterly
direction. They carry brittle crystals of black tourmaline, garnet, and
muscovite mica. East of Ballena the rock becomes coarser and somewhat
gneissose, with an abundance of mica. There are no bedding planes,
simply a parallelism of constituents. This schistose structure has a
northwest direction. The gneiss changes to mica schist on the grade
above Santa Ysabel. The schist alternates with occasional strata of
quartzite; strike north 25° west. The quartzite is a white, fine,
granular variety, containing a little mica. Coarse gneiss outcrops again
farther up the grade; at the top it becomes finer, carrying some
hornblende, and alternating with strata of fine mica schist; dip
northeast. The gneiss often becomes granitoid. The lamination has no
constant direction, and resembles a flowage structure. This granitoid
gneiss extends to within a mile of Julian, when there is quite a sharp
transition to a gneissoid mica schist. That gives place to a fine
schist, and a quarter of a mile west of Julian to a pearly hydro-mica
schist. The schists strike north 20° to 30° west, dip 70° northeast. At
Julian the rock is a dark, thin-bedded mica schist, usually termed a
slate. There are also dark felsitic rocks and some gneisses. The belt of
dark slaty mica schists is about half a mile wide. Toward the Balkan
Mountain the rocks become more gneissoid. This mountain seems to be
formed wholly of gneiss and mica schist. In some places the rock is
nearly massive, and contains a large amount of quartz.
The rocks forming the mountains near the road from San Felipe to
Vallecito are nearly all gneissoid. The real desert begins on leaving
San Felipe Valley. The road extends southeast for 5 miles and then turns
southwest, descending a narrow, rocky gorge to the head of Vallecito
Creek. Near where the road turns to the southwest, the gneisses are cut
by innumerable dikes of coarse granitic composition. Many of these run
parallel, cutting across the strike of the gneisses, and give the
appearance of a bedded formation. In the cañon, before reaching
Vallecito Creek, mica schist appears. It is bent and twisted into every
conceivable direction, and varies exceedingly in structure and
composition in the course of a few feet. The dip is northeast, and often
at a small angle. The granite dikes often carry garnets, being quite
similar to those between Julian and Banner. They were probably intruded
after the eruption of the granite, and the related metamorphism.
At Mason’s granite and gneiss both appear as intrusives in the schists,
and are themselves cut by coarse dikes similar to those described.
Between this point and Banner, in a direct line, gneiss is the
prevailing rock. The high mountain east of Banner is more granitoid.
There is a sandy valley of considerable extent about Mason’s; eastward a
low ridge is crossed, and the road descends to Vallecito Valley between
barren granite mountains, gradually descending until the open desert is
reached. When the granite is hard these mountains are very rugged, but
in places they are covered so deeply with soft, decomposed material as
to closely resemble the Tertiary deposits farther east. The mountains
often show pale purple to brown tints. On examination they appear to
consist of a white granite, which has been so shattered as to break up
into pieces, averaging not over 2 inches in diameter. This rock presents
a very similar appearance for miles, particularly on the north side of
the creek.
At Palm Springs the soft clay beds of late Tertiary age begin to appear.
They dip in all directions, though that to the south and southwest is
the most common. Toward Carrizo Station these are often covered by
granitic detritus. The Tertiary beds widen out where the road strikes
Carrizo Creek, and at Carrizo Station they have a width of nearly 10
miles. They rest against a granite range north of the creek and south
along a long ridge which terminates in Carrizo Mountain. They also
extend a long distance up Carrizo Creek. Four miles below the station
harder sandstones and strata of shells cap the clay hills. This shell
layer near the creek is 10 feet thick and contains pectens and oyster
shells, belonging to the Miocene-Tertiary. The clay hills which surround
Carrizo Station form a veritable Bad-Land. They show many different
colors, and are perfectly devoid of any vegetation. They have been
eroded into a most confused network of hills and cañons, and are so soft
that it is difficult to travel over them. Six miles below this station
and a mile north of the creek there rises a rugged granite range, facing
the open desert. It rises from the desert quite precipitously nearly
2,000 feet, but blends westward into the ridges which run east from San
Felipe. The granite is coarse and deeply decomposed. Sharp, angular
grains of quartz stand out so prominently as to tear anything with which
they come in contact. The thin-bedded shell strata rest against the
slopes of the mountain, and near the southern end rise against the
eastern slope at a very high angle in sharp, jagged points. These strata
rise above the granite ridges at the point where they occur, and dip
fully 70° to the east. (Fig. 11.) Resting on the summit of this granite
ridge, and immediately west of the steeply inclined and jagged points of
the Tertiary strata, is the southern outcrop of a bed of coarse, hard
sandstone, which rises along the summit of the ridges to the north and
dips west, extending down the western side of the range for a thousand
feet or more, dipping at an angle of about 30°. This sandstone outcrops
along the crest of the ridge for nearly a mile. It is, however, not
absolutely continuous, the granite rising through it in places. Near the
southern end it is so highly metamorphosed as to be with difficulty
distinguished from the granite at the contact. In fact, the two
formations have become so intimately united, that a fracture of the
granite made near the sandstone, instead of stopping at the contact,
extends into the sandstone, so that the two rocks break off together.
The contact is so exceedingly irregular that it seemed at first sight as
if the sandstone had been intruded by the granite. Deep, narrow crevices
extend into the granite, and are filled with sandstone. Some granite
bunches are almost inclosed in the sandstone. The most interesting
feature of this sandstone is the presence in it of an abundance of
well-preserved corals of a type fully as old as the Cretaceous.
Fragments of two species of a large oyster and poorly preserved
specimens of univalve and bivalve shells are also abundant. There are at
least two species of coral, many specimens being at least a foot in
diameter. The sandstone is literally filled with them toward the
southern portion of the outcrop. They also extend down into the crevices
and cavities in the granite. The sandstone shows somewhat less
metamorphism toward the north, where it contains some strata of pebbly
conglomerate. The granite is intersected by many veins of coarsely
crystallized feldspar and quartz. From these veins many of the pebbles
in the conglomerate have been derived. At the highest point of the ridge
the sandstone has the greatest thickness. Here it is broken up into
great blocks 15 feet square, piled in the greatest confusion, as if by
an earthquake. One great mass overhangs the almost precipitous granite
escarpment at an elevation of 1,000 feet above the desert. Many
fractures extend from the sandstones through into the granite. The
sandstones, as well as the granite mountains north, have been baked a
dull red color by the intense heat of the sun. To account for the
peculiar position of this sandstone, as well as the steep inclination of
the Tertiary beds at the southern end of the mountain, we must suppose
that an extensive fault has taken place along the edge of the range
facing the desert. The general inclination of the Tertiary beds to the
west and southwest is also evidence of an uplift along this line.
[Illustration: Fig. 11.]
Carrizo Mountain was ascended from the north by following up a wash
through the clay hills. At the foot of the mountain there is a small
outcrop of ancient volcanic rock greatly altered. This rock rests
against the limestone which forms a large part of the north end of the
mountain. The limestone is crystalline in every portion. The strike, as
well as that of the schists and quartzites by which it is inclosed, is
north 30° to 40° west, dip 75° to the southwest. The color of the
limestone varies from white to streaked and variegated. It was carefully
examined for fossils, but no traces of them could be found. The
limestone is, however, filled in many places with the holes of borers,
and one small incrusting coral and one barnacle were found. The
elevation of the north peak is 1,700 feet, and these were found nearly
at the top. Everything points to a great elevation here in times so
recent that the atmospheric agencies have not yet had time to remove the
surface exposed to the ocean waters. Another factor enters into this
time computation, however, and that is that in this climate, where the
rainfall is so slight, a great many years are required to effect slight
changes. Toward the south peak the rock is almost wholly micaceous and
quartzose schists. Judging from the great amount of metamorphism shown
by these rocks, fossils, if they ever existed, must have been destroyed.
At various points on the northern end of the mountain are horizontal
deposits of a soft, shaly sandstone full of fossils, similar to those
found north of Carrizo Creek. The corals are very large and perfect.
Some nearly entire specimens of large oysters were also obtained, but
most of the bivalve shells are represented only by casts. With all the
exploration which has been done, it seems probable that these beds have
never before been seen.
Professor Blake, geologist of the Pacific Railroad Survey, passed up
Carrizo Creek in 1853, but, from the statements made, it seems his
observations were confined to the immediate vicinity of the road. His is
the only geological party that has visited this region up to the present
time. The vicinity of Carrizo Mountain is a favorite one for
prospectors, and every winter it is visited by a number of parties. As
yet no important discoveries have been made, and I cannot say that I
think the region is a favorable one. Silver has been reported from the
southern slope of Carrizo Mountain, and at one time there was
considerable excitement. The mountain, though formed wholly of
metamorphic rocks, does not appear to have been mineralized to any
extent. Only one dike was seen on the mountain, and that was of a
coarse, granitic nature.
There is not the slightest doubt as to the presence of a non-conformity
between the Miocene-Tertiary and the coral-bearing sandstones. Specimens
of the coral were sent to the National Museum, and were pronounced
similar to some from the lowest Cretaceous of Texas. As to the age of
the limestone and associated metamorphic rocks, they are unquestionably
Carboniferous or older. A float piece of silicious limestone was found
containing some shells, but no opportunity for their investigation has
yet occurred. The Tertiary beds are covered, wherever any of their
original surfaces yet remain, by a great variety of washed bowlders.
With regard to the structure of this eastern slope of the Peninsula
range, I can hardly agree with the views before expressed, that there
are to be seen here evidences of an enormous fault, to which the steep
escarpment toward the east is due. The eastern side of the range, so
precipitous in places, has been compared to that of the Sierras in
structure and general features. It is true that this descent is very
abrupt in places, but in others it is almost as gradual as the western
slope. For instance, the gradually descending ridges which extend east
from Banner for nearly 30 miles, show no indication of any fault, save
at the mouth of Carrizo Creek, where there has undoubtedly been a fault
of considerable importance. The very abrupt descent east of the Balkan
and Laguna Mountains is due solely to enormous erosion, for both north
and south ridges extend past them for many miles into the desert.
The San Jacinto Mountains also send out long arms into the desert, and
below the boundary Signal Mountain and a connecting range seem to be
merely a spur of the main system. The rocks of the metamorphic belt at
Julian and Banner, and farther south, dip to the northeast, indicating a
great fold rather than fault, with the most strongly pronounced
intrusive granites and diorites at some distance on each side.
It is not generally known that an ancient auriferous gravel channel
exists in the county. It begins about a mile north of the old stage
station, and 3 miles west of Ballena Post Office, where there rises a
hill shaped like a whale’s back (hence the name Ballena), covered with
washed gravel and bowlders. The main portion of the channel which has
escaped erosion begins south of the stage station, capping a hill which
has an elevation above the sea of 2,400 feet, being a little lower than
the so-called Whale Mountain. The gravel is 50 to 100 feet thick, and
has a width of 2,000 feet or more. It rises 300 to 500 feet above the
valleys and cañons on its sides. It extends in a direction a little
south of west for about 4 miles, terminating on the south of Santa Maria
Valley. A granite ridge runs 2 or 3 miles farther in the same direction,
probably preserved by the gravels, which are now gone. A pretty valley,
a mile long, has been eroded in the eastern end of the gravels, down to
the underlying granite. Placer mining has been carried on for years here
in a small way by Mexicans. Gold is said to be scattered everywhere
through the gravels, which are often very firmly cemented. Lack of
water, for the ridge is higher than any of the surrounding country, has
prevented work on a large scale. Lately a mining district has been
organized, and it is proposed to bring water 7 miles in pipe. In the
gravels are washed bowlders, many of them being 2 feet in diameter and
well polished. The remarkable thing about them, however, is that they
are nearly all porphyries. The most abundant is a red feldspar quartz
porphyry. Quartzite bowlders of all colors are numerous, and there are a
few of the basic diorite so common in portions of the county. Garnets
are said to be very abundant in the gravels, and many bowlders of a
schist carrying them are also present. The matrix of this rock could not
be made out in the field; it is very tough and heavy, and has never been
seen in place. The red porphyry bowlders resemble those on the mesa
farther west, but have never been found in place. Never, in the
mountains east or north, has porphyry of this kind been seen, either by
myself or described by others. From the old stage station the upper
course of the stream was north and south as far as it can be traced.
There are indications that one branch extended easterly toward Julian.
These gravels appear on a hill surrounded by deep cañons, about 2 miles
east of the top of the grade above Foster’s. At the top of the grade the
hills on the west are flat-topped, and covered with gravels to a depth
of 150 feet. These have much the same character, and probably belong to
the same channel. More investigation is needed to determine whether the
course of the old stream was down toward the San Diego River, in Cajon
Valley, or west toward the high mesas south and southeast of Poway
Valley. It seems probable, however, that the stream flowed west, and
that the mesas have been formed partly from the bowlders which they
brought down. This mesa, as well as the gravels at the head of the
grade, has an elevation of 1,500 feet. The source of the porphyry
bowlders and the garnetiferous schists of this old river is a matter of
great perplexity. The gravel deposit has every characteristic of an old
river channel, and not that of an elevated arm of the sea; besides, the
presence of gold in the gravels indicates their derivation from the
country farther east. The gold may have been derived from Julian or Mesa
Grande, or some more remote point. The river must have flowed across the
gold belt, but then the question arises, how could a river of such
magnitude have existed so near the summit? The only way out of the
difficulty is to suppose that a great uplift has taken place along the
crest and western slope, coupled with an enormous amount of erosion; and
that this stream once, before this great change took place in the
configuration of the country, headed many miles to the northeast, far
beyond the drainage of the western slope. The bowlders consist largely
of hard rocks, and are very smoothly rounded and polished, indicating
that they have been transported a long distance, and subjected to
attrition through a protracted interval. It is quite possible that this
river emptied into or near San Diego Bay, and that the immense beds of
bowlder conglomerates about the bay owe their formation largely to this
river action.
The first outcrop of crystalline rocks in Mission Valley is about 3
miles above the old Mission, where the San Diego River enters a cañon.
It is a volcanic tufa, consisting of grayish to greenish fragments of a
fine-grained rock imbedded in a brown matrix. This has a width of about
half a mile. Along the cañon, dikes of a greenish amygdaloid have been
intruded in the rock, and are particularly numerous north of the river.
One of these dikes in the cañon was observed to be amygdaloidal in the
center. Farther up the cañon there is a great variety of tufas. The
first contains feldspathic and hornblendic fragments nearly blended in a
base consisting of crystallized feldspar and dark chloritic particles.
Above this is a dike of brownish crystalline rock, much altered; the
only distinguishable mineral being feldspar, in small crystals. Then
follows another tufa, with nearly blended micaceous fragments. The next
rock is a fine crystalline one with very regular bedding planes, a foot
or more thick; dip 30° to 40° southeast, strike north 35° east. Then
follows a dark, aphanitic, structureless rock for some distance. At one
point a branching dike of almost pure feldspathic material spreads out
into this aphanitic rock in radiating arms. Apparent bedding planes run
through them, as well as the country rock, showing that these planes are
not those of sedimentation, but are due to some secondary cause. These
rocks occupy the cañon for 1½ miles, and are all undoubtedly of volcanic
or intrusive origin. A series of rocks of metamorphic origin outcrops a
thousand feet along the cañon. The first of these is a micaceous
felsite. That is followed by fine-grained granitic rocks carrying
garnets, and this by a hornblendic felsite. The latter finally becomes
mixed and blended with a coarse micaceous diorite, containing a glassy
feldspar. This rock is the chief one exposed through the cañon. It has
granitic and syenitic facies. The tuffs exposed at the mouth of the
cañon extend in a direction a little east of south for 3 miles, until
covered by the mesas which extend west from Cajon Valley. They show a
comparatively uniform character, the fragments being generally nearly
blended. The ridge which these rocks form is separated from the granite
by an elevated mesa a mile wide. The tuffs are exposed along Chaparral
Cañon to within 2 miles of the mission.
The granite ridge at the lower end of Cajon Valley does not extend more
than 2 miles north of the cañon, when it becomes covered with bedded
deposits and bowlders of late Tertiary age. Granite does not appear in
Sycamore Cañon until the northeast boundary of the Cajon grant is
reached. High hills of gravel and bowlders lie east of the cañon and
extend toward Foster’s. The main body of granite is met at the head of
the cañon. It extends along the east side of the road to Poway Valley.
Bunches of dark, coarse diorite occur in it in many places. The gravel
mesa south of Poway Valley has an elevation of 1,200 feet. Small areas
of gravel also remain on the hills northeast of the valley. The granite
ridge, flanked by porphyries, does not outcrop very prominently south of
Los Peñasquitos Cañon. The ridge southwest of Poway Valley seems to be
formed largely of gravels, rising 1,500 feet.
The usual brecciated tuffs outcrop in the gulches and along the creek
just above Los Peñasquitos ranch house. They appear along the old road
to Escondido for 2 miles. A body of chloritic granite appears in the
center in the form of a long dike, extending from the Peñasquitos Creek
a mile or more north of the road. Toward the east the breccia becomes
finer and almost loses its fragmental character. Between this formation
and the granite a dark micaceous felsite, probably metamorphic,
outcrops. The fragments in the tuff are diabasic at times and at others
largely petrosilicious and feldspathic. The crystalline rock on the east
is, perhaps, more nearly diorite than granite, as the feldspar is
chiefly a glassy one. Black Mountain is formed of this dark breccia,
while the high range of mountains which rises on the north and extends
northwesterly between San Bernardino and the ocean, is formed partly of
granitic rocks and partly of the tuffs and porphyries, the latter lying
on the west.
A rolling, hilly country, containing much good land, stretches north
toward Escondido. Remnants of the mesa conglomerates remain in places on
the eastern edge of the Peñasquitos grant. The granite is coarse and
rises in huge, rounded knobs along the road. A little south of San
Bernardino Post Office there rises a conical peak of micaceous diorite.
A somewhat similar rock, but more diabasic in appearance, forms the
mountain immediately west of the Post Office. This formation extends
northwesterly for several miles, having a width of about a mile. The
rock over much of this area closely resembles the gabbros and olivinitic
diabases from the southern part of the county. It is penetrated by
dioritic and granitic veins, in which the structure is often pegmatitic.
At the point where the road stops at the entrance of the cañon of Diablo
Creek, this basic formation is replaced on the west by a massive,
jointed quartz rock, containing a little feldspar and chlorite, and in
places becoming granitoid. It often has a fragmental character, with the
quartzose bodies imbedded in a matrix more granitic, or simply darker
and chloritic. This rock is quite uniform for 3 miles down the cañon,
quartz being the predominating constituent. It is very probable that
this represents an original sedimentary terrain. It is followed on the
western slope of the range by the dark tuffs before described. Here the
matrix is often porphyritic, with a fluidal structure. Portions are real
porphyries. A mile east of Olivenheim it resembles diorite porphyrite.
The last exposure seen on the west was of the usual tufaceous character.
This formation narrows northward, and on the road to San Marcos shows
the width of a mile.
Northwest of San Marcos there is a large body of metamorphic rock,
chiefly felsite schists and feldspathic quartzites. These extend in a
northwest direction toward Buena Vista, but there are not many
exposures. Dark diorite outcrops south of Buena Vista, and extends west
for a mile and a half, when it sinks under the Tertiary deposits. The
last outcrop seen was a dark micaceous diorite. A mile west of this
point there is quite an outcrop of diabase containing an excess of dark
feldspar. The sandy clays extend west from this point to Oceanside. Near
Buena Vista station the diorite is impregnated with green copper
carbonates, and a considerable amount of work has been done, but
evidently no paying bodies of ore were found. Syenite outcrops near
Kelly’s ranch house, and in the hills east. The crystalline rocks come
nearer the ocean here than at any other place in the county.
Between Escondido and Moosa Cañon, granites, with bunches of dark
diorite, are the only rocks seen. A broad, sandy valley extends up San
Luis Rey River to within 5 miles of Pala, when the high granite
mountains close in, forming a cañon. The valley widens at Pala, and for
many miles a broad, sloping deposit of bowlders and gravel borders the
river, and rises high against the foot of Smith’s Mountain. It is often
2 miles wide and represents a great amount of erosion. A mile northeast
of Pala is a high hill of diabase, similar to that in the southern part
of the county. On the eastern slope of this hill is an enormous
pegmatite vein, carrying a very interesting set of minerals. This vein
is twenty or more feet wide, and dips west at a small angle. There are
masses of great size of almost pure mica and feldspar, or quartz and
feldspar—in the latter case very fine specimens of graphic granite have
been formed. Near the southern end of this vein is a deposit of
lepidolite mica, 10 feet thick at the widest part, and appearing in
detached bodies for several hundred feet. It is fine-grained and shows a
pale purple color. In places it is pure, in others filled with large
radial aggregates of pink tourmaline (rubellite). Some of the aggregates
are a foot across, others are long and slender, with arborescent forms.
North of the main deposit it is found in quartz in fan-shaped
aggregates, the crystals being more than a foot long, but greatly
decomposed. Black tourmaline is abundant in the pegmatite surrounding
the lepidolite, but in poor, brittle crystals. Green tourmaline is
present in places in the form of minute grains. Garnets are also to be
found in places. The vein as a whole is inclosed in the diabase.
The western end of Smith’s Mountain shows many bodies of dark dioritic
rocks. The major part of the rock is, however, gneiss and mica schist,
all very easily decomposed, leaving an immense amount of bowlders and
gravel along all of the gulches. Mica schists cover an extensive area
along the southern slope of Smith’s Mountain, on the Pauma grant. These
are undoubtedly a continuation of the schists of the Julian belt, but
carry no minerals. The belt of schists extends nearly if not quite
through to Julian. Warner Valley is located at the head of San Luis Rey
River. It is entirely surrounded by granite mountains. There is not as
great a variety of intrusive rock here as in other parts of the county.
Point Loma forms a peninsula, the greatest length of which is about 6
miles, and greatest breadth, 1½ miles. During Quaternary times it was an
island, but owing partly to an elevation of the coast, and partly to the
detritus brought down by the San Diego River, it becomes joined to the
mainland. It rises 400 feet in almost perpendicular cliffs at its
southern end, gradually lessening in height toward Old Town. The rock of
which it is formed consists of soft shales and sandstones, the latter
often quite consolidated. The strata at the extreme end of the point dip
south, but in a short distance turn and maintain a quite uniform dip to
the northeast nearly the whole length of the peninsula. This abrupt
elevation evidently owes its origin to a fault accompanied by an uplift,
and not to erosion. Beginning at Ocean Beach, and following along the
base of the cliffs to the light-house, hundreds of faults can be
counted. Near Ocean Beach fifteen can be counted in the space of 200
feet. The direction of these faults is nearly at right angles to the
strike. The most of them are nearly vertical and clean cut. The throw
varies from a few inches to many feet. Sometimes the north and sometimes
the south wall has risen. An interesting overthrust fault is exposed in
the cliffs north of Ballast Point. (Fig. 12.)
[Illustration: Fig. 12.]
A conglomerate of late Tertiary age overlies the Cretaceous rocks
unconformably on the extreme end of the point. These conglomerates are
firmly cemented and form high cliffs. They dip at an angle of 30° to the
southeast. The pebbles are in part derived from the sandstone of the
point, and in part from the crystalline rocks east of the mesa. Near the
top of this conglomerate are immense, semi-angular bowlders. These have
rolled down to the beach and are strewn around the end of the point.
Many large ones are to be found a little west of the new light-house,
but the greatest of all is on the eastern side. It is fully 10 feet in
diameter, and formed of the same kind of rock as that on which the mesa
rests 8 miles east of San Diego, viz: a green volcanic tuff. It is a
very interesting question as to how these immense bowlders have been
transported so far and left in the beds near the top of the cliffs. I
can account for it only by supposing that the point with relation to the
country back of San Diego was several thousand feet lower at one time,
and that a river of great volume, flowing over a steep channel, entered
the bay at this place, depositing irregular beds of bowlders. This old
river may have been the same one which formed the auriferous gravel
channel before mentioned. The fault planes on Point Loma extend through
the conglomerate beds, indicating that the elevation took place after
the bowlder beds were formed.
An interesting collection of fossils was gathered from the lowest strata
exposed, and from the bowlders in the conglomerates. This collection
numbers something over sixty Cretaceous species, many of which are new.
The fossils are not abundant, nor are they well preserved. Nearly all of
these are characteristic Chico (Upper Cretaceous) fossils. There is,
however, one species found here in considerable abundance, but rather
poorly preserved, which Dr. White has described under the name of
_Coralliochama Orcutti_, and which he has made the chief foundation for
a new division of the Cretaceous, termed the Wallala Beds. The name was
given on account of the occurrence of this fossil, together with several
other species, at or near Fort Ross, Sonoma County, and also at Todos
Santos Bay, Lower California, where the best specimens were found. These
beds stand in an unknown relation to the other Cretaceous deposits
stratigraphically, but have been supposed, on account of the fossils, to
indicate a division between the Chico and Shasta groups. I believe,
however, that the occurrence of the most important fossil of this
supposed division on Point Loma, in the same beds with undoubted Chico
fossils, destroys the validity of the supposed Wallala Beds.
In a bluff at the northeastern end of the Point Loma peninsula, west of
Old Town, there is a stratum of calcareous sandstone, carrying many
fossils belonging to the Eocene, or lowest Tertiary. The strata dip
northeast at a small angle, and though they cannot be traced
continuously west to the outcrops of Cretaceous rocks, yet from the fact
that they have the same dip, leads me to the belief that the two beds
are conformable. This younger deposit corresponds to the Tejon, or
Division B, of Professor Whitney. Everywhere in the State there exists
the closest relation between the Chico and the Eocene. Here on Point
Loma they are undoubtedly also conformable, but each is distinct as
regards its fauna, for they are separated by nearly a thousand feet of
unfossiliferous strata.
False Bay occupies the basin of a synclinal, for the strata dip
northeasterly from Point Loma and south from the Soledad Hills. A
violent disturbance, forming a great uplifted fold or perhaps a fault,
has taken place along a line extending southeast from La Jolla through
the Soledad Hills. At the eastern end of False Bay there is a small
exposure of Eocene strata, dipping west. Near the mouth of Rose Cañon
the strata dip southwest, and at the mouth of the cañon they dip 40°
northeast. Along the road which leads over the hills to La Jolla the
rocks are tilted at a very high angle to the southwest. The highest
point of the Soledad Hills, rising 700 feet, lies over this disturbed
region. Unconsolidated bowlder deposits lie on the top of the hills. The
strata on the east side of Rose Cañon are well exposed, but do not seem
to partake of the disturbance shown on the west. This is probably no
unconformity, as they contain Eocene fossils, and the Eocene in other
spots appears to be conformable with the Chico. Along the coast between
False Bay and La Jolla the strata dip south at a small angle. At La
Jolla, near the caves, they have been folded so as to dip very steeply
to the southwest for nearly a quarter of a mile across the strike. Near
the eastern end of the cliffs a reversal takes place, and they dip
northeast at nearly as great an angle. Around the little bay there are
no exposures, but a mile northward begins a very high line of cliffs,
which extend through to the mouth of Soledad Cañon. This fold at La
Jolla brings to the surface fossiliferous strata, bearing a number of
species similar to those at Point Loma; among them is the _Coralliochama
Orcutti_. The strata of the high cliffs north of La Jolla dip northerly
at a small angle, and show only a few fossils of the Eocene age. The
cliffs rise fully 400 feet. At the bottom of the cliffs are shales;
higher up are great beds of conglomerate bowlders, chiefly a reddish
porphyry.
Coal is reported to outcrop above the water at very low tide somewhere
along this stretch of cliffs. It of course must occur in strata of
Tertiary age. The coal vein struck in a boring at La Jolla must be
Cretaceous. About 3 miles up the coast from La Jolla, there appears a
dike of basalt cutting the Tertiary shales. At high tide it is nearly
covered by the ocean. It has a course about 30° east of north, and
stands vertical. It begins on the north, close in under the high cliffs,
but does not extend into them, the only signs being a fault in line with
the dike. It is not more than 2 feet wide at the northern point where it
is exposed. It is dark and compact and so decayed as to be easily taken
for an argillite. The walls of the dike are very smooth and regular,
except near the southern point, where it runs into the water. Here it
swells to a width of 30 feet. The edges of the dike are compact, while
the vesicular portion is in the center, where there is often a flowage
structure developed. The central portion is more or less laminated
parallel to the wall, and thus is generally a well-pronounced columnar
structure developed the whole width. The columns lie horizontally across
the dikes and are 12 to 15 inches in diameter. The cavities are wholly
or in part filled with calcite. Metamorphism of the adjoining shales is
apparent for 2 feet away, but the sea water has so decomposed the shale
that it is not so strongly marked as it would otherwise be. The dike
projects above the water in places for a distance of 1,000 feet, making
its total exposed length about 1,800 feet. In the mesa southeast of Rose
Cañon, and along the San Diego River, and back of San Diego, the
formation belongs almost wholly to the late Tertiary. It is not certain
whether the Miocene is present or not. A number of Miocene fossils have
been found in the county, but perhaps the most of them have come from
Carrizo Creek. Many fossils are given in Dr. Cooper’s list, as being
found in the Pliocene of San Diego, which are more characteristic of the
Miocene in other localities. I see no reason for doubting that the
Miocene is present, but so intimately related to the Pliocene as to be
stratigraphically inseparable from it. In the region between Rose Cañon
and the northern boundary of the county, I do not know that Miocene
fossils have been found, but in Orange County they are well
characterized.
The region occupied by San Diego Bay and the mesa back of it is
composed, as far as we know, of Quaternary, Pliocene, and perhaps
Miocene strata. Sandstones characterize the lower formation, and loosely
cemented conglomerates, increasing in thickness toward the mountains,
the upper. These were deposited in a sort of basin, of which Point Loma
and the Soledad hills formed the northern and western borders. Many
oscillations of level have taken place, the most recent being an
elevation of 40 feet, shown by an old beach line on Point Loma. The
shells in this beach are the same as those now living in the adjoining
ocean. It is a peculiar fact that the mesas are slightly higher near
their western terminations than farther east, indicating a recent uplift
along the ocean. Water is scarce through this mesa formation. At the end
of Point Loma there is a strong sulphur spring exposed at low tide. Its
waters may possess medicinal properties, and should be examined.
On the southern shore of False Bay is a large deposit of calcareous
tufa. The central portion is quite pure and a number of feet thick; just
how thick is not known. It extends along the shore some distance, and
often contains bowlders and shells. This is evidently a deposit from
some former spring of great size. The mesas lying west of the extensive
volcanic tuffs have been derived largely from the decay of the latter,
and have heavier soil. North of Soledad they become more sandy, and
maintain this character to the Santa Margarita Creek. This light soil,
however, is being successfully cultivated in many places and for certain
kinds of fruit, without irrigation. The surface of the higher portion of
Point Loma, as well as some of the mesas north, is covered with
spherical nodules, a quarter to half an inch in diameter, of sand
cemented with red oxide of iron. These literally cover the ground in
places so that it is difficult to walk. The origin of these at first
seemed very puzzling, but on examining the face of a cliff on the top of
which these were found, an explanation was reached. They were seen to
grow smaller away from the surface of the ground until a depth of 2 feet
was reached, when they cease. Their formation is due to the oxidation of
the iron in the sandstone, and its segregation in little nodules on the
same principle as the formation of concretions.
[Illustration: Fig. 13.]
The cliffs of Eocene sandstone along the ocean grow gradually lower
north of Soledad Cañon. At Encinitos the cliffs are higher again and for
a short distance the strata dip south, but toward Oceanside they resume
the northerly dip and disappear several miles south of that place.
Faults grow less numerous the farther we get from Point Loma. The mesa
is low about Oceanside; it was either never very prominent or else the
erosion has been great.
On the north bank of the Santa Margarita Creek, near the ranch house, is
an interesting cliff of Quaternary sands and gravel, showing a number of
strata deposited under different conditions on an old beach. (Fig. 13.)
The Tertiary beds north of the Santa Margarita Creek are very different
in outline from those south. Instead of their extending in a gradual
slope from the older mountains to the ocean, there arises in them, near
their western border, a range of mountains, known as the San Onofre
Mountains. These extend parallel to the ocean at an average distance of
2 miles. They rise north of the Santa Margarita Creek and extend to the
San Onofre Creek. They have a gradual slope on the west, rising to an
elevation of 1,400 feet, but are quite abrupt on the east. Los Flores
Creek cuts through the southern end of this range, showing that while
the soft, clayey sandstones between it and the Santa Margarita Mountains
slope only 5° to 10° southwest, the rocks of the range itself dip west
at an angle of 35° to 40°. The formation is a breccia, the fragments of
which are argillitic, micaceous, and hornblendic schists. Some of these
fragments are of great size, one bowlder of hornblende schist being 8
feet in diameter. Pebbles of white quartz and other hard metamorphics
are also present. The soft, coarse sandstone in which the fragments are
imbedded show no traces of any granitic matter. The range was ascended 2
miles north of the Los Flores ranch house, and found to consist entirely
of fragmental schists, such as those mentioned, dipping southwest at an
angle of 45°. The mountains were also climbed at their northern end,
near San Onofre Creek. Here there is a very abrupt escarpment on the
eastern side. The strata dip toward the ocean at a high angle, while the
irregular hills and ridges of soft, light-colored sandstone lying east
toward the Santa Margarita Mountains are nearly level. After a careful
study of the range the conclusion was reached that its origin was due to
a great fault, represented by the very abrupt eastern slope, tilting the
elevated portion to the west at a high angle. I believe that this fault
took place after the deposition of the Tertiary strata. As far as my
observation went the Tertiary beds on the east do not rise to meet the
San Onofre range, as they would to a certain extent if it were present
when they were deposited; on the contrary, they dip toward it. West of
the range the ocean is bordered by very high cliffs of Quaternary clays,
and in only two or three places do the Tertiary rocks outcrop. Small
patches of sandstone outcrop near the road at the western foot of the
mountains; they also dip west at a high angle. Many of the fragments at
the northern end of the range show their derivation from a massive
crystalline rock. The hornblende schists are generally garnetiferous.
Blue glaucophane schists are also very common. South of Mission Viejo
Creek, Orange County, there is an outcrop of rock, apparently in place,
which greatly resembles these schists. Good outlines of these mountains,
indicative of structure, can be seen to great advantage from the San
Luis Rey Mission. On the west slope of the San Onofre Mountains, 4 miles
north of Los Flores, is an outcrop of a garnetiferous hornblende schist,
which certainly appears to be in place. This rises 10 feet above the
side of a gulch, and is fully 20 feet across. One mile north and in line
of strike with the last is another outcrop of similar rock, which is so
large that it certainly seems that it must be in place. The only point
north of the San Onofre where this breccia appears is at Arch Beach,
Orange County. The Santa Margarita Mountains are bordered by very
extensive bowlder deposits, which rise as high as 1,500 feet on their
western side.
The topography of the northwestern part of the county between Temecula,
Elsinore, and the ocean, is very complicated. This section is occupied
by rugged, brush-covered mountains and narrow, deep valleys, with the
exception of the Santa Rosa plateau, where the configuration of the
county has been entirely changed by extensive lava eruptions, stretching
over a distance of 10 miles. This mountain region narrows toward the
north to form the Santa Ana range. The variety of rock formations is
very large. The northern portion is unsurveyed. On the south are the two
large grants, the Santa Margarita and the Santa Rosa. Between these lies
De Luz Valley. The Santa Margarita Mountains extend north and south,
forming the eastern borders of the grant and rising to an elevation of
3,100 feet. The granite of the region about De Luz Valley is far from
being homogeneous. A part of it is undoubtedly intrusive, and a part may
represent an original sedimentary formation. Bedding planes are present
in much of this supposed metamorphic granite, but generally no schistose
structure. The presence of the De Luz warm springs is perhaps due to a
dike of dark, aphanitic diorite, which has cut through the granite in an
irregular manner. A very interesting breccia outcrops in the bed of the
creek below the warm springs. (Fig. 14.)
[Illustration: Fig. 14.]
The fragments are chiefly granite and an aphanitic rock. They are quite
angular, showing only a slight rounding of the corners. Some of the
larger fragments are a foot in diameter. The boundaries are very
irregular. Long arms of the inclosing granite project into the breccia.
The base or matrix varies from a coarse syenitic rock to an aphanite. It
often seems to present a blending of different kinds of fragments.
Besides the large inclusions there are scattered through the matrix
small angular pieces, which are so regular in outline and distribution
as to give to the rock the appearance of a porphyritic structure. The
granite in the hills west of the valley contains much biotite and quartz
in long, rounded grains, presenting a pseudo-porphyritic aspect. This
appearance is characteristic of much of the granite of this section.
Imbedded in the granite are masses of dark aphanitic rock. The lower
granite hills are covered with considerable sandy soil. There are
isolated peaks of a coarse white granite, much like that of the Sierra
Nevada, arranged in some sort of regularity in north and south lines.
One rugged peak of this coarse granite rises 2,500 feet west of the
valley. At the northern end of the valley the bedding planes in the
finer grained granites are very regular; strike north 45° west, dip 65°
southwest. There is, however, no schistose structure present.
A half mile above the warm springs is another conglomerate or tuff,
which seems so related to the granite that the latter must really be
eruptive. In a little valley southwest of De Luz and just east of the
Santa Margarita grant there is a large outcrop of diabase. It has been
intruded in a fine-grained, jointed granite. Farther down the valley, on
the road to De Luz Station, there is a narrow outcrop of black quartz
feldspar porphyry, followed on the east by a dark felsitic mica schist;
strike northwest, dip 60° southwest. Immediately west of the deep canons
which lead down to De Luz Creek, rises the Santa Margarita Mountains.
They consist of a fine-grained granite, verging at times on a quartz
porphyry. The main crest is 2 miles long, the highest peak of which is
nearly 3,200 feet. The rock is perfectly massive, but shows apparent
bedding planes; strike north 30° west, dip 80° northeast. The
porphyritic facies of this formation occur in the western slope. On the
western slope of the main range, at an altitude of 2,500 feet, there is
a plateau-like area of a thousand acres or more of fine grass land. It
is dotted with white oak trees. The western slope of this plateau is
very abrupt and brushy. The formation is partly porphyry and partly dark
diabase and diorite. The most interesting fact connected with the Santa
Margarita range is the occurrence of sandstone at an elevation of 2,600
feet on its western slope. The sandstone occupies very limited detached
areas in the heads of the gulches, and is evidently the remnant of a
once far more extensive formation. The sandstone is largely kaolinitic,
and has evidently been derived from the adjoining rocks. At the foot of
the southern end of the mountains appears very quartzose rocks, probably
of metamorphic origin. Coarse granite has been intruded into them in
small bunches. Granite extends southwesterly in the form of a wedge as
far as the Santa Margarita ranch house, and is there covered by modern
deposits. Between De Luz and Fallbrook the country is gently rolling,
with knobs of granitic rocks projecting here and there. About Fallbrook,
and for some distance east, the granite does not outcrop much, owing to
its easy decomposition. A little east of De Luz Station is a small body
of mica schist; dip 30° east, strike north 15° west.
The road from Fallbrook to Temecula leads through a long, narrow valley.
On either hand rise high mountains of bare granite. Immense bowlders, 20
to 30 feet across, line the valley, having fallen from the cliffs. The
granite here is a coarse rock, rich in biotite, and though great masses
could be obtained free from checks, yet does not seem durable. The
valley owes its origin to a difference in rapidity of decay along
certain lines. On this section there appears no trace of the schist belt
extending northwest from Julian. This coarse granite is undoubtedly
intrusive and has cut it off.
A wholly different series of rocks is exposed in the Temecula Cañon, not
more than 2 miles north of the country just described. This cañon is
deep and rocky, taking a very direct course from Temecula to the ocean.
At the upper entrance there is a narrow exposure of granite. This is
followed by quartzite, dipping 45° southwest. The rocks shortly become
massive and are replaced by dark syenitic ones with an excess of
hornblende. Two miles down, granite appears for a short distance, and in
it a quarry has been opened. The rock can be obtained in blocks of any
size from great masses which have broken off and rolled into the cañon.
Gneissoid rocks soon replace the granite, and these are followed by
hornblendic rocks, which vary from a schistose to a massive structure.
In places they contain feldspar and pass into syenites; in others the
rock is almost pure hornblende. The greater portion of these rocks are
of metamorphic origin. The dip is generally vertical, strike east and
west to northwest. The syenites are followed by mica schists, and these
by coarse biotite granite about 5 miles above Howe Station. In the
granite are many pegmatitic veins, carrying biotite, garnets, and
tourmaline. Fine-grained granite, varying at times to syenite, forms the
rock along the cañon for many miles below this point.
The most interesting geological feature about this northwestern part of
San Diego County is the long plateau, confined chiefly to the Santa Rosa
grant. This plateau lies near the western corner of the grant, and
extends east nearly to Murrieta. The lava is broken up into detached
tables by erosion, which become very strongly pronounced toward the
western end of the flow. The western body of lava is the highest. It has
a length of nearly 2 miles and is broken into three peaks or ridges,
sloping generally a few degrees to the east; height 2,850 feet. There
are two terrace-like tables lower down its southern slope. The lava is,
perhaps, a hundred feet thick at its eastern end, and has been so much
eroded toward the western portion that the underlying sandstone is
exposed along the crest of the ridge, with lava lying in broken masses
along its sides. The sandstones form quite an extensive bed under the
lava flow, being 200 or 300 feet thick, and horizontally bedded,
wherever bedding is present. The upper part is very soft and granular,
the lower portion is hard and stained reddish. It carries many bowlders
6 to 8 inches in diameter, different from any other rock seen in the
adjacent mountains: quartzite mica schist, aphanitic rocks, and some
granitic ones. These are washed smooth. The sandstones contain much
kaolinitic matter, and at one spot show an incipient crystallization. A
number of contiguous grains, over a space half an inch in diameter, show
the same orientation. Near the bottom the sandstones are impregnated
with iron. The western ridge in particular shows a great amount of
erosion. The lava is nearly gone in places, but occurs southward in
scattered outcrops for half a mile. At the northern end the sandstone
rises fully 300 feet above the lava. Lava is present on its sides. Much
of the sandstone closely resembles a granite decomposed _in situ_.
Fragments of the mica schist resemble that in the hills west of
Temecula. Northward half a mile is the deep cañon of the San Mateo. The
country descends very rapidly from the lava ridge, especially so on the
north, where the cañon is fully 1,500 feet deep. It is a number of miles
in any direction to mountains which are as high as this lava-capped
sandstone ridge, and the amount of erosion must have been enormous since
it was deposited. Mesa Redonda has an elevation of 2,750 feet, and is
separated from the lava just described by a valley fully 800 feet deep,
and nearly a mile broad. Mesa Redonda is formed by a lava table,
probably basalt, 150 to 200 feet thick. It is quite precipitous on three
sides. The lava is bedded, dipping 5° to 8° northeast. Underneath is a
body of coarse, friable sandstone, similar to that just described. Some
pebbles and bowlders of lava lie in the upper portion of the sandstone.
The sandstone consists of angular quartz grains and kaolinic matter, and
often presents the appearance as if it had been partly fused by the
lava. In the top of the sandstones are pebbles of quartz, feldspar, and
mica schist. The sandstone shows no bedded structure, but seems to form
a mantle over the hill, following the irregularities of the underlying
granite. It descends 700 feet on the southern slope of the mountains
which rise so abruptly from De Luz Valley. The lava has spread out in
thin sheets on the southern slope of the mountain, descending more than
a thousand feet on the east side of Cottonwood Creek. These thin beds
are not massive, but are formed of angular lava bowlders. The flows were
so thin that they either broke up on cooling, or later through
atmospheric agencies. Fig. 15 is a sketch of Mesa Redonda from the
north.
[Illustration: Fig. 15.]
[Illustration: Fig. 16.]
Cienega Peak lies east of Mesa Redonda and is separated from it by two
gulches opening in opposite directions. It has an elevation of 2,400
feet, and the mesas east rise still less. Sandstone underlies this as it
does the other lava flows. Near the eastern end of the southern slope, a
lava flow has broken out from a basin-like depression which opens
southward, and flowed down the mountain for a mile, descending a
vertical distance of 1,800 feet. It appears to have broken up entirely
into angular bowlders. The stream was probably very liquid, like the
others, and formed a thin flow. It takes a slightly winding course and
slopes often 30°. One short branch appears on the western side about
half way down, and another on the east near the bottom. The lava
descends in successive terraces, like steps, from the crater depression.
The width varies from 500 to 700 feet, terminating in a straight line
about a hundred feet above the bed of the cañon at the head of De Luz
Valley. This distance may represent the amount of erosion since the
stream flowed. There are also cañons worn to some depth on each side.
The surface of the flow is rounding, and appearances indicate that it
descended over a surface not much different from the one now shown. A
large part of the bowlders in the creek for several miles are lava. Fig.
16 shows this lava stream as it lies on the mountain side, and also
Cienega Peak, from which it flowed. These lava beds appear very
prominent from De Luz Valley. The long, winding flow is known locally as
the Oak Ridge, on account of its being covered with oaks, while the
adjacent mountains are barren and brushy. It is hard to reconcile the
appearance of these isolated peaks, with often precipitous sides, and
deep valleys between them, showing a great amount of erosion, with the
thin sheets spread out on the southern side of the mountain in so many
places, which from their position indicate so little erosion since they
flowed. It is possible that the mesas, with the high precipitous cliffs,
represent remnants of an older flow, and yet the lithological character
of the lava seems to point to a single origin. With the exception of the
long southerly flow and another short one west of it, the lava
everywhere presents bluffs on its southern side, with deep gulches
between them. Toward the northeast and east there is a gentle slope. A
large part is coarsely vesicular; dense massive portions are mixed
irregularly in places with the vesicular. The lava table-lands lie
nearly 2,000 feet above De Luz Valley. This abrupt escarpment extends
east as far as the lava does, though less marked. There has either been
an enormous erosion in the region lying south, or a great fault
elevating the plateau. A detached portion of the lava plateau caps the
hills west of Murrieta, extending in a north and south line for a
distance of 2 miles. Whether these detached portions all had their
source in one great flow and have been separated by erosion, or were
formed from different sources, was not fully determined. It seems
probable, however, that the main portions did belong to one flow, from
the fact that they have a uniform slope and are underlaid by similar
sandstone, which may once have been the bed of a stream.
The range of mountains lying west of the valley which extends from
Temecula to Elsinore, also has the appearance of having been elevated by
a fault. From the entrance to the Temecula Cañon, northward past
Elsinore, and along the eastern base of the Santa Ana Mountains, these
abrupt escarpments and indications of a fault become more pronounced.
The eastern part of the Santa Rosa plateau, with its lava fields, forms
the southern end of the escarpment. The valley in which are located the
towns of Temecula, Murrieta, and Wildomar, rises gradually toward the
east. The western portion is very fertile. Artesian water is found at
Murrieta. The eastern portion, which rises toward the granite mountains,
is more gravelly, while east of Temescal there is a stretch of many
miles of these dry gravel hills, probably of Quaternary age. The town of
Temecula has an elevation of 1,000 feet. Immediately west and north of
the cañon there arise hills of metamorphic rocks, having an elevation of
1,800 feet. They are covered with dense brush on their eastern slopes,
but contain some fertile valleys to the west. For several miles the rock
is almost wholly metamorphic. It extends south to the cañon and north to
the lava plateau. It is chiefly a fine, dark mica schist; strike
indistinct but north 60° west, to east and west, dip vertical. On the
west it changes to a quartzite. Dikes of granite cut this rock; one is
noticeable for several miles by its more pronounced croppings over the
hills.
East of Murrieta the granite begins near the boundary of the grant, and
forms a line of barren hills extending northerly. East of these the
country is less rocky and quite fertile. Many springs abound in the
granite through this section. Near the Hot Springs is a dike of granite
porphyry. Numerous bunches of a dark, coarse, dioritic rock are
scattered through the light-colored country granite. They weather away
more slowly than the granite. The metamorphic rocks of the Santa Rosa
plateau extend north to the entrance to the cañon, up which the road
passes to Parker Deer’s. The strike in the cañon is a little east of
north. The metamorphic rocks terminate in a range of hills which form
the southern boundary of the Rinconada. Northward the country is formed
of rugged granite mountains. The Los Alamos opens westward into deep
cañons, which lead down to the coast. A dark dioritic granite is
included in the usual light-colored variety, sometimes in bowlder-like
masses and sometimes in dike form. The metamorphic rocks extend 2 miles
west of Parker Deer’s house. They include mica felsite and dark vitreous
quartzite. They are often intruded by granite bosses and dikes of quartz
porphyry. The lava table-land lies just south of the ranch house. It is
about 40 feet thick, and has underneath a kaolinic stratum 12 to 14 feet
thick, which is impregnated with bog iron; one assay has shown 10 per
cent. This is quite similar to the sandstone under the table-land
farther west, but is less quartzose. A similar deposit, impregnated with
iron, was seen north of Mesa Redonda. The Santa Rosa grant consists
chiefly of broad, open valleys, having an altitude of 1,700 to 1,800
feet, with rocky ridges between them.
On the trail from Santa Rosa to Howe Station, the metamorphic rocks
extend to within a mile and a half of the latter place. They are chiefly
light-colored, granular quartzites. Dikes of diabase and gabbro appear
in many places on the Santa Rosa grant. Ores of gold, silver, and copper
are found in the metamorphic rocks of the grant, but they have never
been developed. Selected samples of galena assay several hundred dollars
to the ton in silver. The veins are, however, small and bunchy, and it
is not probable that they can be profitably worked. The granite varies
from one with mica, as the only dark constituent, to one with much
hornblende. It is uniformly coarse and of undoubted eruptive origin,
judging from the manner in which it has broken through the metamorphic
rocks.
The table-land west of Murrieta is about a mile broad and fully as high
as that near Parker Deer’s house. It is separated from the lava farther
west by a mile of brush-covered hills. The lava was supposed to extend
no farther than the big cañon west of Murrieta, but a close examination
revealed a small outcrop on the hills about a mile south of Wildomar.
The elevation is about 600 feet above the valley. It is perhaps one
fourth of a mile across. In places it extends down the hill nearly one
third of its elevation above the valley. It presents the appearance of
having flowed out of the summit of the hill when it had much the same
form as now, and down over its sloping surface. This eruption is
fine-grained, and not vesicular. Much of it has a conglomeritic
character, appearing to have been broken up when almost solid, and then
cemented. The fragments are more or less rounded and elongated, and are
at times almost blended in the matrix. There are signs of former
solfataric action on the summit, there being a considerable deposit of a
light yellowish material, consisting chiefly of alumina and magnesia.
Under the lava is sandstone 10 to 20 feet thick, composed of quartz
grains and kaolinic matter, exactly similar to that under Mesa Redonda.
It would be easily taken for granite decomposed in situ, but for the
large quartz grains. The sandstone has an apparent southerly dip. It is
very difficult to account for the presence of the sandstone under the
lava, unless we suppose it covered the adjacent country, and was only
preserved by the greater permanency of the lava. Another hill of lava
was found 200 feet lower, about a mile south of this, and west of the
cañon leading up to Parker Deer’s. It occupies a sort of depression
between three hills, with gulches cutting into it between them. The lava
is very similar to that just described.
A long, high ridge running northwest and southeast, adjoining the lava,
is very interesting. It is about 200 feet higher, and covered with dense
brush, as is all the country in this vicinity. The greater part of the
hill is formed of a coarse tuff, whose fragments stand out in sharp
relief on the surface of the huge projecting, bowlder-like masses. The
matrix, which is darker and softer, weathers out, leaving the surface of
the rock covered with a great variety of fragments. Some are scoriaceous
or amygdaloidal, others are very coarsely crystalline and porphyritic
with feldspar or hornblende. Some of the fragments are themselves
tufaceous, containing large masses of hornblende in a dioritic matrix.
On the southern end of the hill, a great variety of dikes intersect the
tufa. This is in all probability the neck of an old volcano, but appears
to have no relation to the modern lavas near it. Owing to the exceeding
difficulty of traversing these hills, the exact relations of the
formations were not ascertained. About 10 miles east of Temecula, near
the point where the creek takes a turn to the southeast and enters a
cañon, there has been another lava eruption, but the time at my disposal
did not permit me to examine it. A great variety of rocks are exposed
along the road from Elsinore to Menifee Valley. For nearly 2 miles east
of the station the rock is a white, glassy diorite, with an excess of
feldspar. At the point where the road crosses the railroad, metamorphic
schists appear. The rock is a fine, dark mica felsite. It is so compact
that it breaks with a conchoidal fracture. A great irregularity in
strike and dip exists; the average strike is a little west of north, dip
northeast. As far as the top of the grade, the rocks are in part
metamorphic and part dioritic. There are many dikes; some fine-grained
granites, others micaceous diorite porphyrites. The hills along the west
side of Menifee Valley seem to be mostly metamorphic, with some bunches
and veins of granite.
All of the mountainous region lying south of the road from Temecula to
San Jacinto is granite or diorite, excepting a strip of micaceous schist
and gneisses near Glen Oak Valley. These strike northwest toward
Menifee.
No opportunity was given me to examine the mountainous regions comprised
in the San Jacinto range. The line of hills lying northeast of the town
and having a northwest direction are composed largely of gneiss and mica
schist, with some bodies of white crystalline limestone. In the line of
strike these hills finally disappear north of San Jacinto Lake, under
Quaternary clays and gravels, which form rather an abrupt rise from the
San Jacinto Valley and extend northerly to the San Bernardino Mountains.
The deposits show a great deal of disturbance. A part of them may be
Tertiary. Dikes of dark, heavy diabase and diorite are common about the
sulphur springs north of San Jacinto.
The hills for a distance of 3 miles north of Elsinore are formed of
slate and mica schists; strike north 70° west, dip vertical to 45° east.
This is a continuation of the same series of rocks exposed on the road
to Menifee. A lenticular body of limestone occurs in these slates about
3 miles north and east of Elsinore. It is highly metamorphosed, has a
gray to dark color, and is traceable for 500 or 600 feet. At one spot a
stratum of quartzite divides it. It was carefully examined for fossils,
but none were found. About 4 miles from Elsinore granitic rocks appear,
followed by dark diorites in the vicinity of the Good Hope Mine. The
Pinacate district, taken as a whole, is rather peculiar. At first sight
it seems to be formed of granite, dark diorite, gneiss, mica schist, and
other metamorphic rocks, arranged in the most irregular manner. The belt
of metamorphics northeast and east of Elsinore is terminated on an
irregular east and west line by these granitic bodies, which inclose
portions of the schists, and extend into the main body as long,
dike-like arms. In the vicinity of the Good Hope Mine the strata of
metamorphic rocks inclosed in the granitic rocks have a north and south
strike, and are traceable for a mile or more. The veins of the Good Hope
Mine are in a dike of light-colored biotite granite. It has considerable
width on the surface, 100 feet or more, but below ground some distance
it is not over 12 feet. On the surface it is greatly decomposed and cut
by numerous small veins, which are so scattered that they hardly pay for
working. Below they unite to form larger veins, generally one on the
foot and another nearer the hanging wall. The latter is more irregular,
often running out at a small angle. The foot wall, a dark compact
diorite, is very regular. The walls are separated by well-defined clay
seams from the vein matter, the decomposed granite. Clay seams also
separate the different veins. The foot wall diorite forms the country
rock indefinitely eastward. The hanging wall is a fine, dark brown mica
schist. The quartz is generally friable, and the granite vein matter
much decomposed. The quartz at a depth of 300 feet carried one third of
the gold in the sulphurets. A small amount of silver is also found. This
vein is located for over a mile; direction a little east of north, dip
65° west. It is remarkable that there is no barren quartz; all the ore
pays for working. In the lower workings the veins become more regular.
The Good Hope is the first mine in this district to reach a paying
basis, and that has succeeded in finding a regular, defined quartz
ledge. About 3 miles northwest is another vein, which has an east and
west direction. It seems to lie wholly in granite, save for a narrow
stratum of mica schist on one wall. The vein is located for a mile, but
no extensive development has yet been made on it. On the hills, a short
distance southwest, is an old Mexican mining camp. Many small veins are
found in the vicinity, generally in a dark micaceous diorite. There are
also bunch-like masses of coarse white granite, blending into gneiss and
the gneiss into mica schist. The strike is exceedingly irregular,
changing from north and south to east and west in the course of a few
feet. Toward Elsinore mica schist, quartzose, and feldspathic rocks
replace the greater portion of the granite. For some distance the
schists are cut up by dikes of fine-grained granite, running in
different directions, and small bunches of the same rock, often only a
few feet across, but sharply differentiated from the schists. Judging
from the exposure here, I think we might say that at the time of the
metamorphism the action was so intense as to change the sedimentary
rocks to mica schists and gneisses and through these to squeeze the
liquified portions of the same formation in dikes and fissures. Small
fragments of mica schist were noticed in the eruptive masses. In a
region like this it is often difficult to draw the line between eruptive
and metamorphic rocks. It has been shown before that lamination is no
sure indication of sedimentary structure.
Lake Elsinore is bordered on the west by a high and rugged granite
range. In the mountains west of Elsinore the granite which cuts off the
metamorphic rocks on the Santa Ana range is again replaced by the
Metamorphic Series, which are here very greatly altered. They strike a
little west of north and dip vertical or at a steep angle to the east.
The boundary of the granite is very irregular, and masses outcrop in the
metamorphics near the main contact line. Much of this crystalline rock
perhaps more truly belongs to the diorites.
The new silver mines lie just north of the San Diego County line, and
west of the divide, a position which brings them into Orange County. The
formations in which the veins occur vary from a dark brown felsite,
often micaceous, to a finely banded quartzose rock. The latter is very
compact, and often almost massive. In places hard, blocky argillites
appear. The two or more veins found here carry galena bearing silver,
and also much magnetite and iron sulphurets, with some of the baser
metals. The veins are characterized by a dark red gossan cap on or near
the surface. Carbonates are found in this. These deposits exist as
impregnations along a fissure, which is not very strongly pronounced.
The ore is usually quite massive. The little gangue present is calcite.
Not enough development has been made here at the time of my visit to
show how extensive the deposits are. The metamorphic rocks extend north
along the mountains, forming the summit and eastern slope for a number
of miles. Granite borders them on the west toward San Juan. It is
probable that this belt of mineral-bearing rocks runs continuously
through to Silverado Cañon. At some time this Elsinore basin opened out
through the Temescal Valley, but now a low divide separates it from the
head of Temescal Creek. Gravel-topped hills lie along the mountains west
of the creek. At the terra cotta works a drill was sunk over 600 feet
without reaching the bottom of the basin. The Cheney Coal Mine is
located 5 miles northwest of Elsinore, in the same basin. The beds dip
to the west and southwest, having clay below, and sandstone followed by
clay above. The coal is 7 to 8 feet thick, generally solid, but in
places showing a parting in the middle. A great deal of faulting has
taken place, but there seems to be no system about it. The throw of the
faults sometimes amounts to 30 feet, often disturbing the pitch of the
vein, and making it greater. The strata evidently belong to the
Miocene-Tertiary, for a little farther down the valley fossils of that
age are found. This old Tertiary valley, undoubtedly an arm of the sea,
opened into the large valleys of San Bernardino and Los Angeles
Counties, and extended southerly to Temecula; though south of Elsinore
the Tertiary is covered by Quaternary gravels. The depth is unknown, but
the width is quite narrow, being from 1 to 2 miles. Not more than a
quarter of a mile northeast of the coal mine the metamorphic rocks,
quartzites, and hard, blocky argillites outcrop. East of Temescal Creek
northward the mountains are formed of a quartz feldspar porphyry of a
dark gray color; at times it blends into portions not distinctly
porphyritic.
Three miles north of the San Diego County line granite appears again on
the east flank of the Santa Ana range and extends north to Cold Water
Cañon. Between Temescal Creek and the mountains is a broad, sloping
gravel and bowlder deposit of great thickness, resting on the Tertiary.
Two miles south of the Temescal Post Office there is an outcrop of soft
sandstone carrying Miocene fossils. It dips southwest at an angle of
30°. Extensive clay banks of various colors and nearly horizontally
bedded lie along the flanks of the mountains both east and west of the
creek. An interesting series of rocks is exposed up Cold Water Cañon.
This cañon has been eroded near the northern termination of the granitic
portion of the Santa Ana Mountains. The first rock exposed is a
micaceous diorite, decomposed to a great depth, but very tough when
fresh. This is followed by syenite. A mile up the cañon, near the
western edge of this rock and wholly inclosed in it, is a small mass of
jasper schist and a lenticular body of semi-crystalline limestone. No
traces of fossils were found in it. West of the syenite is another
diorite dike. Then follows banded jaspery rocks, sometimes verging on
micaceous felsite or quartzites. There are also some slates, and all are
often greatly contorted; strike north to northeast. North of the cañon
these rocks extend to the summit, while south the Santiago Peak, the
highest of the range, and the ridges leading up to it from the east,
consist of a coarse quartzose granite, with but little if any triclinic
feldspar. A variety of dikes occur near the summit north of the cañon,
among them hornblende porphyry, porphyritic granite, and syenite.
Fossils were found on the ridge leading up to the summit, north of Cold
Water Cañon. They occur in a grayish rock, apparently a fine micaceous
felsite. They are poorly preserved, on account of the extreme degree of
metamorphism to which the rocks have been subjected. The rocks have
become so altered by pressure that they will not break on the lines of
bedding, but perpendicular thereto. The fossils consist of impressions
of a small bivalve shell. Only about a dozen specimens could be found.
The rocks are more altered than any others I have ever seen carrying
fossils. These are the first fossils reported from the metamorphic rocks
of the Santa Ana range. These fossils when determined will give a clue
to the age of the metamorphic gold-bearing rocks of this portion of the
State, and also of the granite, concerning which much diversity of
opinion has existed.
Dawson Cañon, which heads in the Temescal Mountains, was explored and
found to contain interesting geological features. A fine opportunity is
given for the study of the relation of the granite to the extensive
porphyry intrusives. For 2 miles east of Temescal Creek no eruptives
appear; the rocks being wholly of the Metamorphic Series, with exposures
of highly altered sandstones, clay shale, conglomerates, etc., striking
northwest and dipping southeast at 45° to 50°. About 3 miles up the
cañon the argillaceous rocks are replaced by a coarse granite, rich in
mica and quartz. This is the prevailing rock up the cañon for 2 miles,
and it apparently extends much farther east. It shows a great variation
in appearance; much of it contains large crystals of flesh-colored
orthoclase. In this granite, particularly on the north side of the
cañon, there are dikes of many kinds of rocks. Large dikes of beautiful
diorite porphyrites, both light and dark colored, appear in places. At
one spot 4 miles from the mouth of the cañon, there are rectilinear
dikes of fine-grained granite, intersecting each other like artificial
stone fences. For the distance of a mile east, after the granite begins
in the cañon, the hills north show nothing but metamorphic schists. The
porphyry in the mountains south does not reach the cañon. The great mass
of this rock is dark, but in the vicinity of the granite it is lighter
colored and more feldspathic, sometimes assuming a granitic structure.
In places it is a gray, hard rock, of almost conchoidal fracture, and
faint feldspar crystals. The granite near the contact is usually sharply
defined, and has a faintly porphyritic appearance at times. The line of
junction of the two formations is sharply defined, not only
lithologically, but physically. It is difficult to say which is the
older. No granite appears in dikes in the porphyry, but there are many
dikes of a porphyry-like appearance, resembling the light-colored
porphyry in the granite itself. The line of junction is very irregular,
and it is certain that the two formations do not belong to the same
eruptive mass.
East of the head of Dawson Cañon there is another outcrop of
considerable extent of metamorphic rock, micaceous felsites, and other
dark schists. A mile west of the Gavilan Mines is a high conical peak
formed of coarse, dark diabase. The mines of this district are in white
biotite granite, continuous with that of the Pinacate district. The
metamorphic rocks south of Dawson Cañon strike east and west, dip north,
and extend in a westerly direction nearly to Temescal Post Office. North
of the cañon, 2 miles from its mouth, there are a number of outcrops in
vein-like forms and in bunches, of a black crystalline material,
evidently tourmaline, identical with that at the Temescal Mine. These
occur in the metamorphic sandstone and shales. The next large cañon in
the Santa Ana range north of Cold Water Cañon shows highly disturbed
Tertiary strata at its mouth, dipping away from the range at a high
angle. They are soft, white clayey deposits, containing small nodules of
selenite. The first of the older rocks exposed in the cañon is a
hornblende porphyry, with variations to a granular diorite. For 3 miles
up the cañon the only rocks seen are crushed and silicified ones of the
Metamorphic Series. They dip, as a usual thing, at a high angle to the
east, though in spots it is to the west or horizontal. Quartzose
sandstones prevail, with blocky argillitic rocks and conglomerates. Near
the summit there are dikes of green tufaceous porphyries.
Temescal Valley is underlaid by clays of a great variety of colors. They
are being used very extensively for the coarser kinds of pottery and
drain pipe. The Miocene deposits of the valley dip westward from the
Temescal range, and instead of also dipping away from the Santa Ana
Mountains basin-like, they dip west into the latter range. The dip of
these beds 3 miles south of South Riverside is 5° to 10° southwest, and
as the Santa Ana Mountains are approached the dip increases, and at a
distance of a fourth of a mile, up to the metamorphics, it varies from
45° to vertical. The strata are not exposed all the distance across the
valley, but there is no sign of a fold or overthrow; everything seems to
point to a gradually increasing dip. This is indicative of an elevation
of the region toward Temescal, or a sinking of the Santa Ana Mountains.
This is undoubtedly the fault line which follows the range for such a
long distance south. Several thin seams of coal outcrop for a distance
of 10 miles along the base of the mountains. They have been opened in a
number of places and all the strata found dipping into the mountains.
The coal seams are often only a few hundred feet away from the
metamorphics, and dip toward them at a very regular angle of 45°.
Judging from the position of the strata it is not probable that the coal
underlies the valley, and as it is so close to the mountains, formed
wholly of rocks of the Metamorphic Series, it cannot be of great extent.
I believe that appearances point to the whole of the coal beds having
been eroded, save the limited, steeply inclined portion at the foot of
the mountains. A crowding of the strata against the mountains during the
movements along the fault line, have given rise to the steep dip. The
highest portion of the Tertiary beds has an elevation of 1,500 feet. A
very even, gently sloping plain extends from this elevation toward South
Riverside. It is formed of unconsolidated wash from the mountains,
deposited on and dipping in the opposite direction from the Tertiary.
The Tertiary formation consists of clays in various conditions of
consolidation, others chalky in appearance, and a great thickness of
argillaceous quartz-sand loosely cemented. Poorly preserved fossils are
found in places. Near the southeastern corner of Mr. Hoag’s ranch is a
hill with hardened concretionary sandstone outcropping around it. Nearly
every portion of this contains fragments of bones supposed to be
cetacean. Artesian wells are obtained near Temescal Post Office at a
depth of 300 feet. The water is abundant and of excellent quality, and
is flumed to South Riverside.
Bunches of granite outcrop in the metamorphic rocks along the east side
of Temescal Creek north of Dawson Cañon. At the dam of the San Jacinto
Company there is a large outcrop of the beautiful diorite porphyrite,
similar to that seen in Dawson Cañon. This extends northwesterly along
Temescal Creek toward South Riverside, where it is quarried. It makes an
excellent and durable building stone, being compact and free from much
mica or hornblende. West of this is a narrow strip of coarse granite,
followed by diabase. North of Mr. Hoag’s ranch, and west of the dam, is
a dike of black porphyry. Westward the crystalline rocks are overlaid by
the Tertiary.
The dam commenced across the Temescal Creek at this point, where it
enters the cañon, was intended to have been extended down to the
bedrock, and thus bring to the surface the water which flowed beneath
the surface channel. The diorite porphyrite is followed on the east by
black porphyry.
_Geology of the Temescal Tin District._—The Temescal Tin Mine is located
in the northern part of the San Jacinto grant, and about 5 miles
southeast of South Riverside. This portion of the grant consists of
rolling hills. On the west is a large body of porphyry, extending nearly
to the Temescal Creek.
The first rock exposed along the road to the mine east of the creek is a
dark flinty one. This is followed by a body of black porphyry, with
white feldspar crystals. The porphyry is about a mile across, and is
followed on the east by massive black crystalline rock, and that by a
felsite. These rocks are soon replaced by granite, in which there are
dikes of fine-grained, highly quartzose granite. Little black veinlets
of tourmaline aggregates are very numerous in the granite, extending
through all the rock up to the porphyry. They have a northeast
direction. The material forming them is the same as the gangue of the
tin veins. A half mile south of the road is a cañon. Here the porphyry
is seen extending up to the granite. The granite is greatly broken near
the contact, and though there is no blending of one into the other,
there is a confused mixture of broken portions of both rocks. Bunches
and dike-like bodies of granite are inclosed in the porphyry. The little
veinlets of tourmaline seem to have replaced the feldspar and mica,
leaving the quartz. These veins grow larger toward Cajalco Hill. Just
west of the works is a great mass of the black veinstone, the gangue of
the tin ore. This rises in high, rugged croppings, and covers an area of
about 300 by 250 feet. This is the greatest body of vein matter to be
seen in the district. The tin deposit worked lies in an eastern
prolongation of this cropping. The course of the veins is north 45°
east, dip 65° to 70° northwest. The country rock is a coarse hornblendic
biotite granite. The vein has the usual character of mineral deposits,
swelling at times to a width of 8 feet, and then contracting to much
less. The highest grade ore is found in the narrower portions, where it
is sometimes almost pure tin oxide, running as high as 70 per cent. The
vein matter does not consist wholly of tourmaline, but contains quartz
grains scattered through it in about the same proportion as in the
granite. The tin is not found in the quartzose part of the gangue to any
extent, but in the irregular vein-like deposits of pure tourmaline,
which lie in the quartzose gangue. The tin occurs in this in bunches and
stringers of nearly pure ore, or disseminated through it. This is
particularly the case where the width of the vein is 6 to 8 feet. Where
it pinches, the whole vein is sometimes formed of the tourmaline
aggregate and tin ore. The vein has usually clay seams on both walls;
sometimes it is frozen to one wall; wherever the walls come together and
cut out the vein matter, the seams remain. The tourmaline vein matter is
an aggregate of needle-like crystals. There are two varieties of tin
ore: the yellow, appearing in thin layers in an uncrystalline form; the
brown, in granular form in the massive specimens, or in small, clear,
reddish brown crystals lining cavities. In the latter case it forms
handsome specimens. A small amount of arsenical pyrites is present in
places in the vein, and iron pyrites in the granite. The quartzose
portion of the vein matter often blends into the granite walls, and
there are bodies of evidently granitic origin wholly inclosed in the
vein matter. A careful study of the vein matter, and its relation to the
walls, shows that it is simply a portion of the granite, in which the
feldspar and dark silicates, hornblende, and mica have been removed and
tourmaline substituted. The quartz has the same character and color as
that in the granite, and many transition stages in the process are
shown. Where the action has been more intense, near and along the
fissures, the quartz has been wholly removed and the tourmaline
deposited, together with the tin. Cajalco was the center of this action.
The veins decrease in size farther away.
At the time of my visit the mine had been opened to a depth of 180 feet,
by two working shafts. The total length opened on the vein is 300 feet.
Two levels have been run and work was in progress on the third. The main
ore body lies in the center of the workings, and extends downward in the
dip of the veins. The ore milled averaged 5 per cent of tin oxide,
though large portions, as before stated, are very high grade. The
company has also prospected Cajalco Hill by tunnel and open cuts, and
one or more of the veins south by shafts. At the time of my visit two of
Husband’s pneumatic stamps were in operation. They weigh 900 pounds
each, and drop one hundred and thirty-five times per minute.
South and southeast of the works are many bunchy veins of the black tin
gangue. They often carry considerable iron. They extend, generally
nearly parallel, in a northeast and southwest direction. Some appear as
mere bunches on the surface. These veins closely resemble the main vein
at Cajalco Hill, and are due to the same action, and it has been
supposed that many of them will be found to carry tin, though it is not
present on the surface. About 2 miles south the granite is replaced by a
banded feldspar porphyry. This cuts off the tourmaline veins. The
granite about the works, and especially toward the contact with the
porphyry, is cut by many dikes of a fine-grained granite, having an
excess of quartz and feldspar. Associated with the porphyry are strata
of metamorphic rocks, of a hard, dark, quartzose character. A quarter of
a mile northwest of the mine is a bunch-like outcrop of porphyry,
carrying silver and copper carbonate. The black veins outcrop for a
distance of 2 miles northwest from the mine, extending into the
porphyry, which replaces the granite in that direction. The granite
extends eastward for many miles.
The general geological features which obtain here are: A semi-circular
area of granite over 2 miles in diameter, surrounded on the northwest
and south by porphyries and joined on the east to a great body of
granitic rocks extending indefinitely in that direction. Around the
border of this granite protuberance are many dikes of a fine-grained
granite. Cutting through the granite in a northeast and southwest
direction are the black tourmaline veins, which form the gangue of the
tin ore when it is present.
Tin occurs here under conditions different from any other known deposit.
Tin veins are almost always found in granitic formations, but such an
extensively developed tourmaline veinstone is remarkable. The direction
of the fissure system shown here is an uncommon one in California. The
veinstone, together with the associated metals, has probably resulted
from a process of sublimation along lines of fracture, removing those
portions of the granite easily affected, over a large area, as at
Cajalco Hill, and in the immediate contact completely replacing it with
the massive aggregate of minute tourmaline crystals.
Thanks are due to the manager, Captain Harris, for the facility freely
afforded me for examining the mine, the works, and the country about.
North of South Riverside the Tertiary beds dip at a small angle to the
north. The Santa Ana River has cut its course through the hills at the
northern end of the Santa Ana Mountains. No outcrop of the metamorphic
rocks appears in the cañon. The Tertiary strata no longer dip toward the
west, but in the Chino hills north of the river show a great anticlinal
arch. Along the south side of the river the beds dip 70° northeast;
farther west, near the heart of the range, they dip 60° southwest,
strike north 30° west. Near the upper end of the cañon there are fault
lines dipping toward the range, which show an elevation of the hanging
wall. Bedrock Cañon is the first large one which opens to the Santa Ana
River from the western slope of the mountains. Opposite the mouth of
this cañon the greatest amount of water appears in the bed of the river,
indicating the presence of hard rock only a little distance below. Coal
veins are located near the head of this cañon, one 700, the other one
1,300 feet above the river. They dip only a few degrees to the
southwest. They are exposed on cliffs facing the mountains to the
northeast. Below them are very hard sandstones carrying fossils,
probably Cretaceous. One prospect shows a number of seams within a width
of 8 feet. The widest is 29 inches, the others much smaller. The other
prospects show only one 39-inch seam. Their position, lying so flat high
on the mountains, indicates an uplift without great disturbance, while
the gypsum mines farther down on the flank of the mountains dip at a
high angle to the southeast. It may be that all of the coal deposits of
the western slope of the Santa Ana Mountains belong to the Cretaceous,
and have been greatly separated by faulting and folding. A deposit of
white, granular gypsum has been opened in Gypsum Cañon, 2 miles south of
the river. The beds have a thickness of 8 or 10 feet. At one spot a
large mass of crystalline dolomite was found. The deposits run with the
strata, north and south, and dip west 60°. As we approach Olive, the few
croppings seen still dip south or southwest, but at a less angle. South
of the mouth of Silverado Cañon a line of hills extends north and south,
bordering the Santa Ana Plain. The western portion of these hills is
formed of basalt considerably decomposed. The basalt varies from
scoriaceous to fine-grained and compact. Its eastern edge was seen to
rest on Miocene sandstones, and it dips west at a small angle, perhaps
10°. The lava seems to have been squeezed up in fissures, judging from
the way in which it outcrops. Its greatest elevation is 800 feet. At
some places the sandstones, where not covered with lava, have been
silicified, turned to quartzite, or rendered granitic in appearance.
This may be due to an intrusive neck of lava, or more probably to the
action of thermal springs.
An interesting fold of the Tertiary strata was observed at the entrance
of Santiago Cañon. The sandstones and conglomerates on the eastern side
dip to the northeast at an angle of 30°, while those on the west side
dip in the opposite direction. The valley has been eroded in the summit
of an anticlinal. The rocks of the eastern side rise again against the
side of the mountains, thus forming a synclinal. Up the cañon the
sandstones on the west maintain a southwest dip of 45° to 50°, and
strike north 40° west. The cañon finally leaves the anticlinal, and the
rocks dip southwest on both sides. Toward the summit of the hill, north
of the Harris Coal Mine, the dip increases to 70°, but on the top they
turn so that the strata lie horizontal. Here they consist of clay shale.
The strata at the coal mine swing around, and one mile northeast they
strike north and south and dip west. This hill seems to form the
southern termination of the anticlinal ridge north of Santiago Cañon.
Southeast of this point there is a simple monoclinal fold or slope away
from the older rocks of the high mountains. There has apparently been a
fault extending northwest in this anticlinal ridge, bringing up the clay
shales which farther south were shown to belong to the Cretaceous.
Harris Coal Mine shows a seam 18 inches wide, shale forming the foot
wall and sandstone the upper. There is a fault of 200 feet cutting this
coal seam. The sandstone at the mouth of Silverado Cañon dips south 30°,
forming bold cliffs. A half mile up the cañon there are heavy beds of
clay shale inclosed in the sandstone. Cretaceous fossils appear in the
shales, as well as in a coarse sandstone which underlies them. This
sandstone is replaced by conglomerates near the contact with the
underlying Metamorphic Series. The sandstone rises to a height of 2,500
feet, with bold, almost perpendicular cliffs facing the mountains.
Portions of the sandstone containing the fossils are often very much
hardened.
The first crystalline rocks met are dark and fine grained, with traces
of bowlder-like inclusions, and are evidently eruptive tuffs. Above
these are green, dioritic rocks. These intrusives are followed for
several miles by sandstone and shale, in which the stratification is
often obliterated. In other places thin layers of sandstone and shale
are wonderfully contorted. The dip is at a high angle either east or
west. In the vicinity of the old Silverado Camp there are dikes and
bunches of a green dioritic rock. The mines in the Silverado district
are again being developed to some extent. The mineral belt is about 2
miles wide, and extends nearly north and south. The country is formed to
a great extent of dikes of greenish to blackish rocks, often showing
distinct hornblende crystals. The dip of the metamorphic rocks is east
about 45°. There is one main mineral vein located, beginning about a
mile north of Silverado, and extending in a southerly direction for 7 or
8 miles. The Quincy Mine is one of the most northern ones. The vein has
a width of 2 feet; the ore, silver-bearing galena in a calcite gangue.
It carries but little base metal of any kind. The ore has a peculiar
appearance, the galena being distributed through the gangue in little
leafy crystals or aggregates. The fissure is well defined and regular,
with a pale green syenitic rock on the hanging wall, and a dark diorite
on the foot wall. This hanging wall rock weathers to a light gray color,
producing a rock known as porphyry among the miners. South of this mine
a side vein carries much antimony. The Quincy has been opened along a
length of 500 feet. The ore is quite uniform, producing one eighth in
concentrates. The Quincy camp has an elevation of 2,300 feet. South of
Silverado Cañon, in Silver and Pine Cañons, a great amount of work was
done during the former excitement. The sides of the steep, rocky cañons
are fairly honey-combed with tunnels, which were undertaken without
sufficient prospecting, and, of course, never struck anything. The New
York Mine spent much money, but did not prove a success. West is the
Princess, and farther still, about 1,200 feet above the cañon, is the
Blue Light Mine, on which much work has been done and rich ore taken
out. The mines south of the cañon are in a feldspathic rock, which
weathers white. It is undoubtedly an intrusive porphyry, for traces of
feldspar crystals are to be seen. The mines are characterized by a large
amount of zinc-blende, iron pyrites, and not a large percentage of lead,
making them more difficult to reduce. The porphyry is mineralized in
many places where no traces of the precious metals occur. Litigation and
poor management seem to be the chief factors in stopping work in this
district. Though some of the ore runs into hundreds of dollars to the
ton, the most of it is medium to low grade.
About a mile and a half down the cañon from the old Silver Post Office,
and in a cañon coming in from the south, is a cropping of dark, somewhat
argillaceous limestone inclosed in shales. The limestone does not seem
to have been highly metamorphosed, yet the fossils which it contains are
almost obliterated. The faint impressions are those of coral stems,
stromatopora, and some other low forms of life. Half a mile farther down
the cañon is a cropping of brecciated marble. At many points,
particularly on the north side of the cañon, there are great masses of
apparently conglomeritic character, but with a crystalline structure.
The matrix has a green to brown color, and in it are imbedded pebbles of
the same degree of fineness, but often distinguished by much brighter
red, purple, and green colors. In this cañon, as in others of this
range, the water holds much lime in solution, and extensive tufas are
frequently to be seen. The basal members of the Cretaceous at the mouth
of Silverado Cañon consist of conglomerates passing up into sandstone,
and those into shales; dip 55° away from the mountains in the highest
ridge, but in the course of a quarter of a mile becoming much less. The
change in dip is very sharp, giving the appearance of a fault.
A cañon which enters Silverado Cañon from the northeast near its mouth
was followed up nearly to its head for the purpose of investigating some
limestone outcrops. The first outcrop in this cañon is the usual dark
porphyry. Beyond this the stream has cut a deep cañon through an immense
conglomerate of porphyritic and quartzose pebbles. The porphyritic
pebbles are dioritic and part red and black porphyries. Some of them are
similar to dikes farther up the mountains. Through this great
conglomerate bed there are dikes of black porphyry, with pale feldspar.
Tufaceous porphyries form a large part of these dikes. The base is
purple and the pebbles light green, or the reverse. These conglomeritic
porphyries differ from the great beds of sedimentary origin, in having
all the pebbles of a uniform character with a crystalline matrix. The
sedimentary beds contain pebbles of all sizes and description, in a
matrix of small pebbles or coarse sand. Farther up the cañon the great
body of the rock is crushed shale and black to gray sandstone; dip
vertical, inclining most generally to the east, strike north and south.
Two miles up the cañon is a dike of diorite porphyrite, coarse in the
middle and fine on the edges. Four miles up is a stratum of gray
limestone. More outcrops appear on the north side of the cañon, but
whether they belong to the same stratum or different cannot be told, on
account of the crushing undergone. These deposits are bunchy, swelling
in one case to a width of 100 feet. It is not crystalline. The color is
from black to gray. It contains fine specimens of a bivalve shell, and
faint traces of corals and univalve shells. These beds are said to
extend to the summit, and undoubtedly further examination would reveal
more fossils. Several specimens were sent to the National Museum and
pronounced Carboniferous in age. We have here, then, the first
announcement of the age of the Santa Ana range. This range stands in
such intimate relation to the granite and crystalline schists farther
south, that an approximate determination of the latter is made possible.
Professor Whitney and others following him have classified this range as
Cretaceous. Their grounds are utterly untenable stratigraphically, but
this discovery of Carboniferous fossils makes the evidence of greater
age certain.
On the eastern side of the range, near its northern end, the sandstones
were observed to be silicified, being filled with a network of quartz
veinlets, exactly similar to the silicification of the metamorphic rocks
of the Coast Range proper.
The lowest Cretaceous beds are between Silverado and Williams Cañons,
but the fossils are very similar to those generally found through the
Cretaceous of this region. The lowest beds are a duplicate of those seen
at the mouth of the Silverado Cañon, though apparently a thousand feet
lower in the series. Between the two beds there is another conglomerate
stratum, carrying bowlders different from any seen in the Santa Ana
Mountains. Many of the porphyry bowlders in the basal Cretaceous
conglomerates resemble the porphyry about Temescal. The Santa Clara Coal
Mine, at the mouth of Silverado Cañon, is undoubtedly in strata of
Cretaceous age, though no fossils are found in the strata above till the
Miocene is reached. Up the Santiago Cañon as far as Madame Modjeska’s
place, the fossils are chiefly confined to the eastern side of the
cañon, but the character, dip, and strike of the strata on both sides
are the same. The Cretaceous is separated from the metamorphics by a
line of cross cañons. The highest portions of the Cretaceous terminate
in a line of hills with sharp eastern escarpments.
Shrewsbury Cañon comes in just below Modjeska’s. After passing the
Cretaceous, through which the cañon has cut, the Metamorphic Series was
seen to consist of slates and sandstones, followed by light-colored
granitic rocks, chiefly hornblende and triclinic feldspar. The
metamorphic rocks generally dip to the east.
A mile above Modjeska’s the Santiago Cañon cuts through bold cliffs of
Cretaceous sandstones and conglomerates, and higher up still has eroded
a cañon in the Metamorphic Series. The cliffs, a little back from the
stream, rise probably 1,000 feet. Sandstone belonging to the Metamorphic
Series outcrops in the cañon for some distance, and is followed by
conglomeritic porphyries, containing purple and red bowlders. In some
places the inclusions are angular. These rocks are extensively developed
about the Santiago Mines and higher up in the mountains.
Just below the Alma Mine, on its western side, the creek has cut through
dikes of diorite, which are coarse in the center and fine on the edges.
On the hill south of the Alma Mine the diorite is on the opposite or
eastern side of the vein. Although the exposures are poor, all the
crystalline rocks have the character of intrusives. No blending into the
metamorphic rocks has been noticed. About 3 miles up Shrewsbury Cañon
several claims are located on the southern continuation of the veins of
the Silverado district. Near the head of Santiago Cañon these again
appear well defined, and considerable active work was going on here at
the time of my visit. The veins here have a direction a little east of
south, dipping to the east somewhat less than 45°. It appears that the
mineral belt follows a certain line, generally quite regular, without
any particular reference to the dikes and bunches of intrusives
scattered irregularly here and there. The fissure system has taken a
comparatively regular line and the walls may or may not be intrusive.
The Alma Mine, the northern claim of the Santiago Silver Mining Company,
has been worked by the former operators in a very irregular manner. The
veins and stringers as far as exposed lie wholly in the crushed
quartzose argillites. A tunnel is now being run to open what is supposed
to be the main vein, several hundred feet farther east, and which has
syenite on the hanging wall. Other tunnels are being run along the
creek, one near a body of granitoid rocks, others in slate or quartzite.
The ore is a leafy galena, arranged often in narrow bands with the
crystalline orientation different in alternating bands. Sometimes it
occurs in the form of large solid bunches. Thus far the ore deposits
have been found quite irregular, but it is thought that the main body
has not yet been reached. Very little base metal is present. South, on
the hill, the Morrow claims have been bonded by the same company and are
being opened. On the summit of the hill diorite lies on the eastern side
of the veins. Down the southern slope the veins lie wholly in
metamorphic rocks; the foot wall being more silicious, the hanging
argillaceous. The mineralized portion has a width of 20 feet. A small
vein occurs in the upper side, and a heavier one, sometimes reaching 3
feet, on the foot wall. There are occasional stringers in the crushed
portions between. The gangue is calcite, with some quartz, all mixed
with the broken clayey slates. More zinc-blende and iron pyrites are
found here, also a little antimony. In the Alma Mine the richest galena
is very fine, and sometimes resembles antimonial ores.
South of these mines, toward Trabuco Cañon, another claim is being
worked. South of the Trabuco the conglomerates hide the lode, except at
one spot, where it appears and has been worked. The Cretaceous formation
grows lower as the Trabuco is approached, and does not appear prominent
south of it. In all probability it is covered by the Tertiary, for the
elevation and consequent erosion have not been as great in this
direction.
SAN BERNARDINO COUNTY.
By W. H. Storms, Assistant in the Field.
No portion of California has more diversified mineral wealth than the
county of San Bernardino. Although its area is comprised largely of
rugged mountains and desert waste, yet this county is a producer of
gold, silver, copper, lead, and tin, and contains mines of zinc, iron,
and manganese, besides deposits of borax, salt, soda, baryta, gypsum,
sulphur, onyx, marble, asbestos, and structural material, granite, and
sandstone of great beauty and value. Within its borders are found a wide
range of geological formations from Paleozoic (if not Archæan) to
Tertiary, and a great variety of rocks of igneous origin.
The mines are scattered all over its thousands of square miles of
territory, and have already added millions of dollars to the wealth of
the State and the world. Many of its mines are of phenomenal richness,
and were it not for the expense and extreme difficulty attending
transportation in the desert, San Bernardino County would undoubtedly
take first place in adding to the mineral wealth of California. The
largest and most productive section in the county at present is
THE CALICO MINING DISTRICT.
No region affords better opportunities for the study of a certain class
of ore deposits occurring in eruptive and fragmental rocks than may be
found in the Calico District. The mines, condemned at first, came
quickly to the front nevertheless, and have for the past twelve years
been steady producers of silver bullion. The district is situated 6
miles north of the Atlantic and Pacific Railroad, the nearest station
being Daggett.
GENERAL GEOLOGY OF THE REGION.
The geology of the Calico Mountains at first sight looks simple enough,
but a more thorough investigation quickly convinced me that there were
structural problems to be studied of more than passing importance, as
they seemed to have a bearing upon the extent of the ore deposits. The
most complex region is that immediately about the town of Calico, in the
vicinity of the mines. The balance of the mountain area is more simple.
In a general way the Calico uplift consists of a core of massive
rhyolite, overlying which are heavy deposits of light-colored breccia
and tufa. Along the flanks of the range, and in some places extending
well up into the mountains, are accumulations of undoubted sedimentary
origin, sandstone, sandy shales, and argillaceous rocks, which, with
some local exceptions, dip away from the central mass on all sides
toward the desert plain. While in the district I made some notes on the
general geological features, but not having sufficient time at my
disposal to complete these investigations, I have determined not to
present my views until I have had an opportunity to investigate the
region more carefully.
Subsequent to the uplift of these mountains, erosion has carved deep
cañons and removed great mountain masses. The central area is now
entirely denuded, whereas it was at one time covered with from 100 to
200 feet of tufa and upward of 1,000 feet of sedimentary strata. Not
only have these more recent accumulations been removed, but a large
amount of the hard, dense liparite has also been disintegrated and
carried away by the violent storms which are characteristic of the
desert. Faults are very numerous throughout that portion of the
mountains lying along the south side of the range. They extend for at
least 10 miles in an easterly and westerly direction. The mines occur
along this faulted zone.
The rocks of the region are a violet to brown rhyolite, often
porphyritic; green, yellow, and white tufa; yellowish and greenish
breccia; a greenish gray, fine-grained rock, which has been called
hornblende andesite by Mr. Lindgren, and a yellowish or buff to light
gray felsitic rock, which may be either rhyolite or an older felsite. It
is extremely difficult to distinguish between these rocks, even with the
aid of thin sections under the microscope. I think, however, upon
structural grounds, that I may call the rock felsite. As this is one of
the important questions upon which I have not thoroughly satisfied
myself, it will be left until such time as I have opportunity to make
the necessary investigation.
THE ORE DEPOSITS.
The formation of the ore deposits in the Calico District has been a
subject of much discussion, and the question has received the closest
study and thorough investigation. In my opinion, the ore deposits were
formed through the agency of percolating waters carrying mineral
solutions, which deposited their contents along fault planes and in
certain zones of the country rock, where its brecciated and crushed
state offered superior conditions for the deposit of the silver ores and
the accompanying baryta. That all of these ore deposits have a common
genesis I do not doubt, whether they occur in the liparite, in the tufa,
or in the “mud” overhanging country rock, as is the case at the
Bismarck, Humbug, Waterloo, and some other mines. The form of the
deposits differ somewhat, it is true, for we find the reticulated veins
in the King Mine; the segregated deposits in the Odessa and Waterloo;
the fissures in the Langtry, in West Calico, and the impregnated deposit
in the Humbug. However, all the deposits of the district, of whatever
form, I believe are due to a common cause, having been deposited in
their various forms from mineral-bearing solutions which derived their
contents from the neighboring eruptive rocks (the liparites and tufas),
part of the material doubtless arising from great depth, and a portion
coming from the adjacent inclosing rocks by what is known as lateral
secretion. It is almost an impossibility to find in the Calico region a
piece of rock that does not contain more or less silver, from a fraction
of an ounce per ton upward.
The phenomena of ore deposition was very thoroughly investigated by
Messrs. Louis Janin, E.M., John Hays Hammond, E.M., Ross E. Browne,
E.M., and Wm. Irelan, Jr., State Mineralogist, at the time of the
lawsuit of John S. Doe vs. Waterloo Mining Company. These gentlemen all
agreed upon the origin of the ore deposits, and their opinions coincide
with my own and are in accordance with the ideas expressed above. The
wide difference in the size and form of the many ore bodies does not in
any manner conflict with the theory that in each instance the primary
cause of the deposit was a fracturing and crushing of the rock masses
and the subsequent infiltration of mineral solutions, which precipitated
their contents in the zones and crevices thus prepared for their
reception.
[Illustration: _SKETCH SHOWING
DISTRIBUTION OF ORE ON THE SURFACE IN THE
SILVER KING MINE
AS IT OCCURS BETWEEN THE FAULT PLANES
CALICO MINING DISTRICT
SAN BERNARDINO CO. CAL.
COPIED FROM EXHIBIT “R”
COURT RECORDS IN THE SUIT OF
JOHN S. DOE VS. WATERLOO MINING CO._]
In the Silver King Mine occurs a perfect network of veins, concerning
which Mr. Hammond testified: “At the time of the uplifting of the
liparite, or at some subsequent time, a fault occurred, which separated
a wedge-like mass of liparite from the main mountain mass, and this
fault plane was generally conceded to be what might be termed the foot
wall of the mineral belt, or zone, or lode. Contemporaneously with this
faulting a second fault occurred, which separated the overlying brown
tufa from the liparite, which fissure forms the overhanging wall of the
mineral deposits of the Silver King Mine. At the same time cross
fissures were formed in the liparite mass between the two main fissures.
Thus there was a main fissure or plane of contact between the brown tufa
and the liparite, and a similar fault plane between the segment of
liparite broken off and the main mass of the mountain. Between these two
main fissures, and throughout the whole mass of this segment of liparite
were innumerable fissures, some similar and equal in size to the main
fissures, and others forming a finer system of fissures and cracks,
extending through the rocks in all directions, leaving it in a broken
and disintegrated, and in many places an almost pulverized condition.
Although these finer fissures generally had a parallelism with the two
main fissures bounding this segment of rock, yet, in many places, these
finer seams or fissures run in every direction through the rock, forming
a network, or reticulated mass. The mineral-bearing waters have
deposited throughout this mass, from wall to wall, the minerals now
found within this zone in the form of baryta, carrying silver. The
finding of baryta in the shattered planes of the liparite, which is
entirely foreign to the rock itself, is sufficient evidence that a crack
or space must have existed prior to its deposition, from the solutions
which penetrated this broken zone of a once massive rock formation.”
[Illustration: _CROSS SECTIONS OF
SILVER KING MINE
TAKEN FROM COURT RECORDS IN SUIT OF
JOHN S. DOE VS. WATERLOO MINING CO._]
[Illustration: REPORT STATE MINERALOGIST
W^M. IRELAN, JR.
STATE MINERALOGIST.
VERTICAL CROSS SECTION
SHOWING THE FORMATION OF THE
SILVER KING LODE
CALICO MINING DISTRICT.
SAN BERNARDINO CO. CAL.
COPIED FROM EXHIBIT “P”
COURT RECORDS OF
JOHN S. DOE
VS.
WATERLOO MINING CO.]
[Illustration: STATE MINERALOGIST’S REPORT
W^M. IRELAN, JR.
STATE MINERALOGIST
_SKETCH MAP SHOWING THE FAULT SYSTEM
OF THE CALICO MINING DISTRICT_
PARTLY TAKEN FROM A MAP
BY
W. LINDGREN, E.M.
BY
W. H. STORMS, E.M.
ASSISTANT IN THE FIELD.]
The Odessa Mine offers good illustrations of impregnated masses, as does
also the Waterloo. In each of these mines, as in many others, the ore
bodies are found in bunches or pockets, varying from little deposits of
nominal value to great ore chambers containing thousands of tons of pay
rock. In these cases, as at the King Mine, a system of faulting planes
marks the general strike of a mineral-bearing zone or lode, but the
great rock masses of tufa, in which these ore bodies occur (and also of
sandstone in the Waterloo), are quite loose and porous in texture, and
undoubtedly the ore bodies in these mines resulted partially, at least,
from the impregnation of the rock with the mineral solutions which found
an easy passage along the fault planes that had cut the rocks in every
direction.
In the Waterloo Mine one of the fault planes exhibited a regularity
seldom seen in any mine. It coursed through the light-colored, soft tufa
in an easterly and westerly direction, was perfectly true, and as smooth
as any hard-finished wall could be made by the most skillful artisan.
The fracture was of knife-blade thinness, and its sides were coated with
dark red iron oxide. It dipped to the southward at an angle of about
40°. At one time it was considered to be the hanging wall of the lode,
but a miner broke through the wall to cut a hitch for a timber and it
was found that the overlying rock beyond the slip was ore-bearing also.
Stopes in this mine were frequently over ten sets in width, or over 60
feet. At the eastern end of the claim some extremely rich ore was mined
from a belt of jasper, a metamorphosed clay shale, which by heat and
pressure had become an intensely hard, fine-grained, flinty rock, yet
some of this jasper contained over 1,000 ounces of silver per ton.
In West Calico, 2 miles west of the Waterloo, is the Langtry group of
claims. The principal development is on the west end of the Langtry
Mine. The Langtry may be called the anomaly of the camp, as it is a
fissure vein pure and simple, or, more strictly speaking, two fissures.
The strike of these two fissures, which are 60 feet apart, is nearly
parallel, but they will undoubtedly meet in depth. That on the south
side dips northerly, while the other pitches toward the south slightly.
Both stand at a high angle, and it is doubtful if they will converge
inside of 250 feet from the surface. The veins are composed principally
of a coarsely crystallized baryta with quartz, containing brown iron
oxides, lead carbonate, ochre, manganese oxide, and chloride of silver.
The average value of the ore was about 22 ounces per ton. The veins vary
from a thin seam to over 10 feet in width on the north vein, having an
average width of 3 or 4 feet. These veins occur in the “outside” or
“mud” country, which lies along the flank of the southern slope of the
Calico Mountains. The mud shales and argillaceous sandstones here lie
nearly horizontal, the veins cutting them at an angle closely
approximating 90°.
SUSPENDED MINING OPERATIONS.
The low price of silver during the past two years has resulted
disastrously to the mining industry in Calico District. The great
Waterloo, for many years the largest producer, and employing not less
than 150 men in mines and mills, was closed down, as it seemed foolhardy
to exhaust the great ore bodies when the profit derived from the
extraction and milling of the ores was merely nominal. For years these
mines had kept the sixty-stamp Boss process mill and the fifteen-stamp
pan mill at Daggett busy night and day, but in the spring of 1892 the
stamps were hung up and the mines closed, awaiting better prices for
silver.
The Silver King Mining Company (limited), of London, has continued to
operate, dropping twenty to thirty stamps night and day, under the
superintendency of William S. Edwards. The King Company owns or controls
three important groups of mines in this district, viz.: the Odessa, the
Oriental, and the Occidental. The Odessa made a record during the early
history of the camp by the production of ores of high grade. The policy
which was pursued in those “palmy days”—to gouge out the rich ore
whenever it could be found, without regard to future condition of the
mine—left most of the mines in very bad shape. The Odessa is now
recovering under the new management, and the property is being
systematically opened, and it is thought all the ore can be extracted.
In this mine are stopes from which thousands of tons of ore have been
mined, and there is not a stick of timber of any kind in them.
These old stopes are being cleaned out, new levels opened, and good
results are expected in the future. What applies to the Odessa in this
respect is true to a great extent of every other large mine in Calico.
They were all worked in a hand-to-mouth sort of fashion, and although
many of these mines paid handsome dividends, little of the money was
ever put back in anything like permanent improvement. All seemed to
share a common opinion—that the deposits were superficial, and would not
go down, and as a result no one felt like laying out money in an
extravagant and unwarranted manner. But the mines have gone down, and
the men in charge of the mines to-day can see the result of the mistaken
economy of the early operators, and see in Calico an era of recovery of
low-grade ore bodies and development work which is calculated to give
the mines greater apparent permanency than ever heretofore. December 1,
1891, the King mill was enlarged by the addition of ten stamps, making
thirty in all. The Boss process of continuous amalgamation was also
adopted.
CHLORIDING THE MINES.
A system of leasing portions of mining claims, called “chloriding” in
Calico, was introduced in the early days, and is still in vogue. Many
poor men have made moderate fortunes in the district, and in days gone
by all did well. The mines are leased on a royalty of one fourth to one
sixth of the ore to the claim owner, according to its value, the owner
receiving more as the grade is higher. Chloriders were at work on the
Loo, Little Waterman, Humbug, Bismarck, Blackfoot, and other mines,
during the past year. The ore obtained in this manner is usually sacked
and shipped to a custom mill, where it is crushed, the charges ranging
from $9 to $12, according to the character of the ore, some (the more
brittle) milling much faster than others.
THE WATERLOO MINE.
The Waterloo property consists of four claims. The principal workings
are in the Waterloo Mine, where large stopes have been extracted, though
considerable amounts of ore still remain in sight. An idea of the extent
of some of these Calico mines may be gained from the fact that the great
ore body of the Waterloo is 1,100 feet in length, and is known to extend
from the surface down to the 525-foot level. At the east end the
ore-bearing zone is from 4 to 7 feet in width, widening downward. Going
westward it increases in width until it is 60 to 70 feet wide. This
mine, like those immediately about Calico, was worked for rich pockets,
and, as a natural consequence, the mine was left in bad condition. Jos.
D. Kerbaugh, the last Superintendent of the mine, had inaugurated a
systematic method of extracting ore and recovered much lost ground. The
ore is usually low grade, and this, in connection with the low price of
silver, has resulted in the closing up of the mines. A narrow gauge
railroad has been in use for several years to transport the ore from the
Waterloo group and the King and Red Jacket Mines, owned by the same
company, to their mills at Daggett, timber and supplies being brought to
the mines on the return trips. The transportation of ore, I was
informed, cost 12 cents per ton. The railroad is about 7 miles in
length, and runs on a pretty steep grade.
THE BORAX MINE.
In the upturned sedimentary beds which flank the Calico Hills, dipping
outward toward the desert plain on all sides of the uplift, except where
purely local disturbances have caused a reverse condition, are bedded
deposits of calcium borate and gypsum (calcium sulphate). Five miles
east of the town of Calico is the largest known deposit of calcium
borate in the district. The bed, or vein, as it is called, was
discovered some years since, and finally passed into the hands of the
present owners, the Pacific Coast Borax Company, whose extensive works
are located at Alameda, near San Francisco.
GEOLOGY OF THE BORAX DISTRICT.
The borax mine occurs as a bedded vein in the sedimentary strata, which
in Tertiary times were uplifted in the Calico range. The sediments are
composed of sandstones, sandy clays, and clayey sands, comprising a
succession of heavy-bedded, deep-water deposits, and shallow-water,
thin-bedded shales and sands. These variations in the character of the
strata are numerous, and mark the many oscillations of the region, whose
rising or sinking either submerged the strata beneath the waters of a
deep lake, or lifted them until the water flowed over the mud flats only
in thin sheets, which, exposed to the rays of the sun, sometimes
evaporated entirely. Climatic conditions doubtless also were an
important factor in the history of these strata, which are upwards of
1,000 feet in thickness.
Underlying the sediments are the tufas of the Calico region, and beneath
them is found the mass of liparite which underlies this entire region.
The sediments are not materially different from those in the immediate
vicinity of Calico. The rocks have not suffered in the region about the
borax deposit the slightest metamorphism.
The borax vein is traceable for several thousand feet, striking along
the western and northern side of the largest sedimentary hill in the
range, and finally passing down a cañon to the eastward, where it
becomes a well-defined vein. Toward the western end the borate of lime
appears to be much mixed with the sandy sediments, gypsum, and clays,
giving the appearance of having been formed near the shore line of the
basin in which this great mass of material has been left as a residuary
deposit, due to the evaporation of the water containing the calcium
borate.
To me it seems that what is now one of the most valuable deposits of
mineral in the State was at one time the site of a Tertiary lake of
considerable but as yet undetermined size. That although subjected to
the same oscillations as the remainder of the region a basin formed, in
which the waters collected, carrying with them the mineral salts derived
from the rocks of the neighboring country. That finally the climatic
conditions became such that the supply of water was less than the loss
by absorption and evaporation, and the waters of the lake slowly
diminished, it finally disappearing entirely, leaving on the floor of
the lake a thick deposit of calcium borate of snowy whiteness.
After the deposition of the borax bed a general subsidence of the region
occurred, the waters of the great Tertiary lake once more covering the
whole country. Again the sands and finer sedimentary material—the
erosion of the mountains—were carried down and found a resting place on
the floor of the lake, the borax bed being finally covered with several
hundred feet of this detritus. Now, as the same formation in which the
borax mine is found, and even the lower members of the rocks of that
age, are seen resting upon the high ridges and on some of the peaks of
the Calico hills, it would seem highly improbable, to say the least,
that these sediments were built up from the ruins of the Calico
Mountains themselves, but their source was in more distant ranges.
Besides the regular vein-like deposit of calcium borate found at the
borax mine, there are numerous small veinlets in other parts of the
district in which calcium borate and gypsum are found filling cracks and
cavities, probably as the result of infiltration. So common are these
small fissures and beds of borax and gypsum that that portion of the
sedimentary strata lying east of the town of Calico is usually spoken of
as the borax formation by the miners of the district. To thoroughly
investigate all the phenomena connected with these wonderful deposits
and their mode of formation would require more time than was at my
disposal.
As has been previously stated, remnants of the sediments are still found
lying high up on the flanks of the mountains, and even far into the
interior of the hills, and there is every probability that the entire
region included in the Calico District, as well as the country for many
miles around, was at one time buried a thousand feet beneath these
stratified rocks.
With the uplift, the strata inclosing the borax mine were tilted and
folded, and now the sheet of white calcium borate which once lay
glistening in the sun on the bed of a desert dry lake stands like a
great vein traversing the country. There are apparently two of these
veins in close proximity to each other, but I believe them to be one and
the same, being repeated as the result of an anticlinal fold. An ideal
cross-section of the borax mine is here given (p. 347), showing the
nature of the folding at that point; it is not drawn to a scale, being a
sketch only.
To the southward of the mine is seen a large mass of liparite, which has
been pushed up from below. I had not the time necessary to trace out the
line of fracture, but I am of the opinion that it occurs on the line of
the great fault shown on the map of the fault system of the region.
The borax vein is from 7 to 10 feet in thickness Where it has been
exposed in the underground workings. The mineral is the variety of
calcium borate called colemanite, named in honor of Wm. T. Coleman. It
occurs in glassy crystals, some of them having large faces. Many
handsome specimens of this mineral are on exhibition in the Mining
Bureau museum. The mineral is mined in the same manner as ores of gold
or silver. Inclined shafts are sunk on the vein, drifts and levels run,
and the stopes carried up as in any other mine.
[Illustration: _LONGITUDINAL SECTION OF BORAX MINE
CALICO DISTRICT SAN BERNARDINO CO._]
The material, when hoisted to the surface, is loaded in great wagons
hauled by twenty animals and taken to Daggett, where it is shipped to
the works in Alameda. The process of extracting the boracic acid from
the rock as practiced in these works is not given to the public. It is
known that the mineral is crushed and bolted like flour, after grinding
with burrs, but the subsequent treatment is not known outside the works.
To the Superintendent, J. W. S. Perry, I am indebted for a sketch of the
underground working of this remarkable mine, which is reproduced above.
AGE OF THE UPLIFT.
The geological age of the Calico uplift has not been accurately
determined, though there is little doubt that it occurred during the
Tertiary age, probably the Oligocene.
THE IRON MINES.
In this county, about 16 miles in a southeasterly direction from
Newberry Station, on the A. & P. R. R., and 28 miles easterly from
Daggett, are the greatest deposits of iron ore on this coast. They
consist of immense beds or masses of hematite and magnetite ore,
containing a high percentage of iron, with traces only of sulphur and
phosphorus. These mines have been known for many years, and they have
had numerous owners by relocation and purchase, but nothing has yet been
done with them. Iron men from Pittsburg and Cleveland and elsewhere have
visited these mines and secured samples, and all reported favorably on
the excellent quality of the ores, but there the matter was dropped.
Located 16 miles from the railroad, and probably 20 miles by any
possible line of railway survey, as the grades are heavy, with neither
fuel nor water, the problem of their reduction was so formidable that
none dared face it, and for years this magnificent property has been
waiting for some one with capital and a “process” to come and make the
vast wealth available.
THE LAVA BEDS DISTRICT.
This interesting region has come quite prominently into public notice
within the past two years. The district is located in a small range of
mountains about 35 miles east of the Calico range. The nearest station
to the mines is Lavic, on the line of the A. & P. R. R., from which
point the mines are 9 miles distant by a good wagon road. Like most
other desert mining regions it is destitute of timber, and water is not
abundant, though obtainable in the dry lake basin 3½ miles from the
mines. The district was discovered about nine years since, and numerous
claims have been located. The work of development has been confined to a
few of the most promising claims.
GENERAL GEOLOGY.
The mountain range in which the mines of this district occur is isolated
from all others, although evidently a part of a chain extending in a
northwest and southeast direction for many miles. This particular group
of hills is about 4 miles in length by 1½ in width, and consists of
rocks, which are all of plutonic origin. They are mostly quartz porphyry
of the normal type, consisting of a fine-grained felsitic ground mass,
with macroscopical crystals of quartz and feldspar.
Of several thin sections made for the purpose of microscopic study of
these rocks, their behavior under the microscope is so similar that
general description will suffice for all. The section is characterized
by a micro-crystalline to micro-granular ground mass, sometimes to
globulitic. The feldspars are so completely clouded as to leave little
clue to their identity. Some still show faintly the parallel lines which
are so characteristic of plagioclase, but some of these feldspars are
probably orthoclase. These feldspars are plainly distinguishable in the
rock mass with the unaided eye. Quartz blebs as large as small peas,
with many smaller ones, occur plentifully in all of these rocks. In the
section they seem to have been corroded, the outlines being nearly
always rounded, though frequently showing hexagonal forms. Most of these
quartz grains polarize in brilliant colors. All of the quartzes contain
a great abundance of fluid inclusions, some of which show included air
bubbles. Numerous very small, colorless, needle-like crystals, which
occur in all the quartz, are no doubt apatite prisms. Green, dust-like
hornblende as inclusions are not at all uncommon, and in one section a
mass of green, fibrous material, having all the optical properties of
hornblende, is seen. This inclusion is large enough to be easily
distinguished with the unaided eye. There are numerous globulitic,
granular, and sac-like inclusions of the ground mass in many of the
quartzes, which is characteristic of the quartz porphyries generally.
Besides these macroscopic crystals of quartz and feldspar are many
hornblendes, some of which are of good size, a few having the typical
crystal outlines. It is usually of a bright green color, strongly
dichroic, and polarizes in the usual colors. Some of the hornblende is
altered to chlorite. Borders of iron ore, probably magnetite, are
common, frequently preserving the original outline where the hornblende
has suffered great decomposition.
Dark-green basic dikes, which seem to be greatly altered diabase, occur
in the district, but have no connection with any of the ore deposits as
far as observed.
Numerous dikes, large and small, of a red felsitic rock, occur
throughout the district, and seem to bear an important relation to some
of the ore deposits. All of the rock is much decomposed, and its
identification is not an easy matter. It appears under the microscope to
be a finely porphyritic rock, having a somewhat fluidal structure, as
shown in the arrangement of the numerous small, lath-like crystals of
feldspar. Small blebs of quartz occur quite abundantly. In a general way
the rock resembles some rhyolites.
On the northern flank of the range immense masses of red and brown tufa
occur, besides great flows of black basaltic lava. These rocks form a
terrace-like ridge that extends for several miles along the base of the
mountains. Two large cinder cones, one on the northeast end of the
range, the other about 4 miles distant in the desert valley to the
northward, form prominent landmarks.
The basalt is coarse to fine grained, usually black or dark gray, and is
often scoriaceous. It contains plagioclase, augite, and olivine, and
abundant magnetite in a micro-crystalline or granular base. Near the
foot of the range the basalt has overflowed the beds of tufa, which
latter, it is said, contains from a trace to as high as four ounces of
silver per ton. As far as I have any knowledge of it, no prospecting has
been done in these tufa beds, but the fact that silver exists there at
all would lead one to believe that under proper conditions ore bodies of
great value may occur.
At the base of the mountains, at an altitude of 1,800 feet, is a dry
lake, which drains a large area of country. In this basin water has been
obtained by sinking a well 80 feet in depth. Though the well is located
near the edge of the basin, there is little doubt that sufficient water
can be obtained in this basin for milling purposes.
The principal vein in the district lies along the north side of the main
range, and is known as
THE IMPERIAL LODE.
This great vein, the outcrop of which may be seen for 20 miles, is a
“fissure” in every sense of the word, though not a simple one, for it
has numerous divergent branches of considerable size. The main fissure,
however, is strong and constant, and outcrops boldly for nearly 8,000
feet. It varies in width from 4 to 18 feet. It is everywhere well
defined and often shows a banded structure.
The great fissure strikes north 70° west, and dips 65° to 70° to the
south. It occurs in the quartz porphyry, which at contact with the vein
is usually much decomposed and often shattered and crushed, probably
owing partly to the intrusion of a large dike of the red felsitic rock,
a tongue of which has cut across the vein about 3,500 feet from its west
end. This dike follows the vein for some distance on the hanging wall
side coming from the east, gradually nearing the vein until it finally
reaches the fissure, cutting the vein in two. Farther westward it again
appears on the hanging wall side, showing itself at intervals to the
extreme western end of the vein, which comes to an abrupt termination.
This felsitic dike is but one of a number that occur in the immediate
vicinity.
[Illustration: _THE IMPERIAL LODE LAVA BEDS DISTRICT
SAN BERNARDINO CO. CAL.
VEIN CUT BY INTRUSIVE DYKE OF FELSITE_]
Since the formation of the Imperial lode there has been considerable
movement within the vein itself. Slips are numerous, the slickensides
showing plainly. The fault planes, as far as observed, are confined
within the limits of the vein; however, at no place, excepting where the
dike intersects it, did I notice any lateral displacement.
Usually the vein is distinctly separated from the inclosing rock, a clay
selvage marking the line of the fault plane on either side. In some
instances, however, where a brecciated condition of the quartz porphyry
is found in contact with the vein, the ore has been deposited to some
extent in this broken mass, and in such cases the line of demarkation is
not at all plain. These occurrences, together with the branching spurs,
seem to indicate perfectly the character of the vein, which before the
intrusion of the felsitic dike was more simple than we now find it. My
conception of the Imperial vein is that a great fissure formed in this
mountain range; that at the time this disruption occurred the hanging
wall side of the fault slipped downward, causing a further fissuring and
crushing of the rocks on that side of the fault. It is a notable fact
that all the branches or spurs of this vein occur in the hanging wall
country and are directly connected with the main fissure. This idea is
still further substantiated by the additional fact that all, or nearly
all, the crushing and grinding adjacent to the fault plane has occurred
on the hanging wall side.
Occasionally, in the narrower portions of the vein, a banded structure
indicates the probability that the ore now fills what was at one time an
open crevice, which slowly filled with ore by precipitation from the
mineral waters passing along the fault plane.
At one point on the course of the vein, where it is joined by one of the
branching spurs, the felsitic dike has intersected the smaller vein. The
occurrence is plainly seen in a cut made at this place, where rich ore
was found.
[Illustration: _THE FELSITE DYKE
CUTTING A BRANCHING VEIN
IMPERIAL LODE_]
It will be noticed that both the main vein and the spur occur in the
quartz porphyry, and that the red felsite cuts the smaller vein. The
displacement on the surface along the strike of the vein is nearly 40
feet. This does not show in the cross-section.
Since the formation of the Imperial vein the mountains have suffered
great erosion; the highest point along the croppings rises fully 800
feet above the neighboring cañons.
THE ORE.
Although the Imperial vein is a fissure of great length and depth, all
the material that is included between the porphyritic walls is not pay
ore. The ore occurs in shoots of greater or less extent, the same as in
any other vein. The gangue is chiefly quartz, having a pearly luster
resembling in appearance some light grayish lead carbonate at a casual
glance. Accompanying the quartz, though in minor quantities, are baryta,
calcite, and black manganese oxide. The value of the ore lies almost
wholly in its silver contents, which occur as chloride and sulphide
(argentite) accompanying pyrites, chalcopyrite, and iron oxides. The
silver sometimes occurs with copper glance in small bunches in solid
masses of lead carbonate. Such ores are very high grade. In one of the
branches gold is found with only a small percentage of silver, the
reverse condition, however, usually obtains. The silver frequently is
found in the same shoots with the base ores and in quartz without any
intimate association with either lead, copper, or iron. The galena is
sometimes very low grade, carrying only 4 ounces per ton in silver. In
one shoot the lead carbonate contains over 200 ounces. It is a notable
fact that no good ore is found in quantity without copper in some form,
either as sulphide (glance) or carbonate. Chloride of silver is also
found associated with iron and manganese, without copper or lead.
THE CLAIMS ON THE VEIN.
There are six lode claims located on the Imperial vein, on all of which
considerable work has been done. Beginning at the east end, the vein
shows itself on the mountain side close down to the desert wash and not
far distant from the basalt flow on this side of the range.
The most easterly claim is called the Sampson, and from it has been
shipped some rich ore, the claim producing the highest grade ore, I am
told, of any mine on the vein. This claim is joined on the westward by
the Morning Star, a deep cañon separating them. From the bottom of this
cañon it is 800 feet to the summit of the mine, 1,500 feet farther west.
The Morning Star Mine has been quite extensively opened by tunnels and
shafts, but for several years past assessment work only has been done,
as the ore which was found was too low grade to make shipping
profitable.
The Meteor, Mammoth Chief, and Desert Queen succeed each other,
respectively, going west. On the Mammoth Chief and Meteor, a great deal
of work has been done; and it is claimed ore was shipped approximating
$40,000 gross value. At any rate the owners have developed their claims
and made a good living at the expense of the ore thus shipped from the
vein. On the Meteor a shaft has been sunk a depth of 100 feet, at the
bottom of which a drift 40 feet in length has been cut along the vein on
an ore shoot which was followed down from the surface. At another point
on this claim a shaft of 65 feet in depth has been sunk in ore. A drift
at the bottom of this shaft is also in ore, 8 feet of which is exposed
and the foot wall not yet reached.
The ore at this point is said to average 30 ounces. I was told that the
average of the ore throughout the mine was about 25 ounces, ranging from
12 to 75 ounces, and occasionally much more. Numerous cuts, shafts, and
drifts, some of them of considerable size, have been made along the vein
on the Meteor and Mammoth Chief for a distance of 800 feet, and although
these workings are not connected they have the appearance of being on
one shoot of ore. One fact is very evident from an examination of the
mine, and it is one of considerable importance. It is, that the ore is
of better grade and occurs in greater quantity in the vicinity of the
felsitic dike, which, though undoubtedly later than the vein itself,
seems to have enriched the ore very materially. The largest shoot of ore
I saw has formed very close to the point of intersection of the felsitic
dike with the main vein. On the Desert Queen a long tunnel and several
crosscuts have exposed ore bodies, some of which contained upwards of
200 ounces silver per ton.
The Imperial lode is one of the most promising veins of which I have any
knowledge, but it requires considerable capital to properly and
systematically open it. The rock is extremely hard, and the lack of wood
and water are drawbacks which prevent the owners from working the mine
as it should be worked. It would be difficult to find a vein offering
greater natural advantages than are found here, excepting as to wood and
water, both of which are obtainable under the usual conditions attending
that problem on the desert. Water can be found in the dry lake 3½ miles
distant by road, and 1,160 feet below the level of the cañons which cut
the vein.
Coal may be delivered at Lavic Station, 5 miles from the lake, for about
$9 or $10 a ton. The difficulties are no greater than at Calico, where
they seem to have been overcome quite easily. Tunnels may be run in on
the vein, getting average backs of about 350 feet above the bottom of
the cañons.
Should ever this great vein be worked on a larger scale with abundant
capital, a tunnel started at the lake will cut the vein at an average
depth of 1,500 feet. Such a tunnel would probably be about 12,000 feet
in length. The ore shoots seem to have an average width of about 5 feet
as far as exposed, and none of the workings in ore have ever reached the
bottom of a shoot. It is one of the most imposing looking veins I ever
saw. On the Desert Queen the soft hanging wall has been eroded, leaving
the vein standing exposed for fully 80 feet in height.
THE TIPTOP MINE.
About 4,000 feet south from the Imperial lode there is a mine of unusual
character and interest, called the Tiptop. Originally a silver mine, it
is now producing a high-grade copper ore, which is being shipped to
Swansea, Wales.
The Tiptop was discovered in 1890, by the strong outcrop of an ore
shoot. The country rock on both sides of the vein is quartz porphyry,
similar to that inclosing the Imperial lode. The ore occurs along a
fault plane, or rather a series of parallel faults, as the result of
substitution of ore for the original rock. The faulting of the rocks has
resulted in an extensive crushing and breaking up of the porphyry along
the line of fracture, exposing large surfaces of rock, thus facilitating
the deposition of mineral. As mentioned above, the faulting seems to
have consisted of several fractures, nearly or quite parallel, between
which the rock was crushed or ground to powder. In places this ore body
would seem to possess well-defined walls, but moving in either direction
along the strike of this zone the “wall” proves to be simply a faulting
plane, beyond which ore again occurs. The result of these parallel
fractures is to give to the deposit an appearance of banded structure,
like that sometimes noticed in simple fissure veins. This apparently
banded structure is entirely due to the planes of displacement.
[Illustration: _CROSS SECTION
OF
TIPTOP MINE_]
Doubtless this faulting extends to great depth, though the
mineralization is not continuous along the surface for more than 150
feet. At some distance, however, and in line with the strike of the
displacement, other ore bodies appear. The ore body where the discovery
was made is heavily mineralized with iron oxides, of red, yellow, and
black colors.
Much of the original rock has become silicified and bleached to snowy
whiteness in the lower part of the deposit, but such masses contain only
finely disseminated iron pyrites, low grade in silver. The once
sulphuretted ores are so thoroughly oxidized in this surface deposit
that they are very porous.
The ores carry on an average about 30 ounces of silver, and for the most
part are very free-milling. At the time of my visit an estimate of this
silver ore on the dump and in the mine placed its value at,
approximately, $20,000. In one portion of this rather remarkable ore
deposit considerable quantities of native sulphur occur, associated with
a brownish iron oxide and silicious gangue material. As depth is
attained the oxidation is less marked, and at 80 feet has apparently
given place entirely to sulphuretted ores and silicious rock, low in
silver.
The strike of this shoot of ore is north 50° west, dipping northeast at
an angle of 70°. At the depth of 65 feet below the croppings, in sinking
a winze, which in its downward course follows a slip northward but is
vertical as compared with the dip of the vein, a bunch of high-grade,
partly oxidized copper ore was discovered. Further development
discovered other pockets or bunches of copper ore carrying usually about
15 ounces in silver per ton. When a depth of 120 feet had been reached a
crosscut tunnel was run in 235 feet. The course of this tunnel is north
5° west. The face, however, had not reached a line representing the dip
of the surface shoot. The tunnel has been connected by winze with the
upper workings, and considerable other development accomplished.
By means of these workings the peculiarities of the mine have been
exposed. The series of faults which have resulted in the deposit of a
considerable quantity of silver ore have been accompanied by another
series of fractures which, while independent of the former, were,
perhaps, contemporaneous. The second series exhibit no parallelism, but
strike in various directions. Along these fault planes occur bunches of
copper ore, principally variegated pyrites (bornite), chalcopyrite, and
a black “earthy” sulphide, having a shining streak, not sectile,
probably a variety of copper glance.
These ores are sometimes associated with iron sulphide, but most of this
class may be easily sorted. One class of ores occurs intermingled with
the gangue containing about 15 per cent copper. This ore can be
separated on any concentrating machine such as a jig, the resulting
product being high grade. The ore shipped to Swansea has averaged over
33 per cent copper and 15 ounces silver per ton.
[Illustration: _LONGITUDINAL SECTION OF TIPTOP MINE
LAVA BEDS DISTRICT SAN BERNARDINO CO._]
The Tiptop consists of two claims. The easterly one, the Kenton, has
little or no development, though copper carbonates have been discovered
on the ground. All of the workings of the Tiptop that are in copper ore,
it should be remembered, are in the country rock on the foot wall side
of the series of faults in which the silver ore occurs, and no drift or
crosscut had been run into that zone below 80 feet from the surface. The
face of the drift on the third level had exposed about 6 feet of good
ore at the time of my examination. The drift at that point was 160 feet
from the surface. It is not likely, should a crosscut be run under the
silver ore shoot from the lower levels of the mine, that oxidized ore
will be found at that level, but it will be interesting to know what
sort of ore may be found there. Indications of copper on the surface are
very slight. In a few places stains and thin seams of copper carbonates
occur in the fracture joints of the country rock, but there is nothing
to lead one to believe that ore lies beneath that will bear shipment to
Europe and return a handsome profit to the owners of the mine, yet such
is the case.
THE GLADSTONE GOLD MINE.
Less than a mile from the Tiptop, in a northwestern direction, is
another property, the Gladstone, locally known as Halberg’s Gold Mine.
It was located several years ago, and after some development was
practically abandoned, but afterwards came into the hands of the present
owners, who have developed the ground quite extensively, built a long
tramway and ore bins, and established a camp.
Nothing was being done at the time of my visit. The mine is something of
a curiosity geologically and mineralogically. The ore body, for there is
only one of any consequence developed, occurs in the gray quartz
porphyry common to the region. A fault has also occurred here,
fracturing the country rock in a manner similar to that in the Tiptop,
excepting that here there is but a single, simple fault. The ore body
consists of a mass of crushed and broken country rock, portions of which
still show distinctly the original porphyritic structure. Generally
speaking, however, the original rock has undergone an extreme
metamorphosis, resulting, in most cases, in more or less complete
mineralogical and physical changes. The porphyry has, by gradual
replacement, been changed to solid ore, or been silicified to a dense
quartzose, sometimes jaspery, rock. Kaolinization of the feldspars has
also taken place. As to the origin of these deposits there seems to be
little reason to doubt that the ore was deposited by percolating waters,
which derived their contents from the neighboring eruptive rocks. These
solutions were carried into the fault plane, and reaching the great
chamber or crushed mass, found conditions of a superior nature for the
precipitation of the minerals they contained. In the pulverized or
finely crushed portions the ore deposition has been most complete,
entirely replacing the original rock, while in the brecciated portions
the ore occurs as incrustations, filling the smaller interstices, but
sometimes penetrating the rock fragments themselves.
The ore body is something over 200 feet in length and 30 feet or more in
width at the Widest part, but thinning out rather irregularly toward the
ends and also downward.
Doubtless it at one time extended some distance upward, but that portion
has been eroded. Along the plane of the fault the line of demarkation
between ore and porphyry is very distinct, as the two bear not the
slightest resemblance, but at the outer edges of the deposit no such
line can be discovered. The mineral gradually disappears, leaving only a
brecciated mass of whitish rock, which graduates into the normal
porphyry. The brecciated condition of the mass is made more plain by the
variety of color assumed by the angular fragments. They are various
shades of green, red, white, and brown, or yellow, caused by copper
carbonates and iron oxides.
Though the original condition of the ore was doubtless sulphide, it now
contains, as the result of oxidation, hematite, limonite, magnetite,
malachite, azurite, chrysocolla, cerussite, wulfenite, chloride of
silver, manganese oxide, and metallic gold. The value of the ore lies
principally in the gold contained, though in one portion of the ore
body, near its eastern end, rich chloride of silver ore is found, with
but little gold. The physical appearance of the ore is no criterion of
its gold contents, as two pieces, with identically the same
characteristics, will differ widely in value. One may contain $2 or $3
in gold, the other several hundred. Should ever a mill be erected in the
district, this ore can be worked to a profit, though this single ore
body will alone scarcely justify the construction of a mill.
On the south side of this fissure or slip is a vein which runs nearly
parallel with the chambered vein above described. This vein can be
traced for several thousand feet. In character the ore is similar to
that found in the Imperial lode. Assays running over $200 in gold have
been obtained from this ore, and $50 assays are not uncommon. The vein
is quite small, ranging from a mere seam to 2 feet. Scarcely any
development has been done on this vein, though it promises better
results than the large “vein chamber.”
The developments on the Gladstone consist of a shaft 60 feet deep. The
first level is cut at a depth of 30 feet from the surface, where drifts
have been run for a distance of 30 feet each way from the shaft, on the
course of the vein, and a crosscut, 28 feet north. East of this, a
15-foot shaft has been sunk in a good sized cut. A large open cut, 100
feet long, has exposed the upper portion of the ore deposit perfectly.
Other superficial work has been done at various points along the vein. A
tramway of 1,700 feet has been constructed from the mine to the bottom
of an adjacent cañon.
OTHER CLAIMS.
In the vicinity of the mines described in this district are numerous
other claims, some of them having considerable development, but all
lying idle at the time of my visit. One claim has an 80-foot tunnel, and
shows some lead and silver ore of good grade. This claim is patented.
THE ALVORD MINES.
Twenty-three miles northeast from Daggett are the Alvord Mines. The
property has changed hands several times, but is now owned by a party of
Pasadena capitalists, who have under consideration the reconstruction of
their mill, which was burned in September, 1891.
The property consists of six full claims located on one mineral-bearing
zone. The strike of the belt is a few degrees south of west. The mine is
well equipped. The company also owns a millsite at Camp Cady, on the
Mojave River, 9 miles distant from the mines, and valuable water rights
at Paradise Springs, 11 miles northwest from the mines, and a spring
about 1½ miles east of the camp, which is used for camp purposes only.
The mines lie along a broad zone or belt of crystallized carbonate of
lime (calcite), which may be seen for many miles traversing the
dark-colored inclosing rocks. A huge dike of porphyritic rock cuts
across this belt at an angle approaching 90°. The principal
mineralization of the lode occurs east of this dike.
The country rock is described by F. R. Burnham, E.M., formerly the
Superintendent, in his report on the property to the company, as rock
more or less schistose in character, through which, at frequent
intervals, are intruded eruptive dikes. At the east end of the belt is
an accumulation of tufa and basalt. The belt dips south at an angle of
75°. The mineralized portion of this lode extends from the porphyry dike
east through three full claims, disappearing finally beneath the
eruptive rock and desert wash. The dominant point on the lode is 550
feet above the base of the hill.
The entire lode is gold-bearing, some of the iron rock being extremely
rich; gold also occurs in the calcite, though it is usually of a lower
grade than where accompanied by the iron. Iron sulphide containing gold
has been discovered, indicating plainly the origin of the slag-like iron
ores and limonite found on the surface.
To Mr. Burnham’s report I am also indebted for information concerning
the value of the rock, tonnage, and bullion output to date. He has given
arbitrary figures for shipments aggregating $37,000, and an estimate on
$13,000 more, making a total of $50,000. This ore was milled mostly at
the Camp Cady mill and at Hawley’s mill.
An arrastra was used in the early history of the mine. The average
assays made on a ten days’ mill run just prior to the burning of the
mill returned $12 75 per ton. Tailings, during the same period, averaged
$1 25. Bullion produced, $1,430. It was found very difficult to sort the
ore, though it varied constantly in value from $2 to $20 per ton. About
90 per cent of the assay value, it is claimed, was saved in the mill. In
looking through a daily record of assays made in July and August, 1891,
I find them to range from a trace to as high as $1,750, most of them
running from $6 to $18. Mr. Burnham figures 184,000 tons of mill rock in
sight, including all grades, besides large amounts presumed to be
available, but not blocked out for stoping. The value of the ore is
placed at $5 to $6 throughout.
The cost of milling this ore is placed at $2 50, and mining at 50 cents
in large stopes. Should the company now controlling the Alvord Mines
determine to rebuild their mill it will doubtless again become a bullion
producer.
ORO GRANDE DISTRICT.
The Oro Grande Mining District is located immediately east of the
Southern California Railroad, at the town of Oro Grande. It is commonly
supposed to embrace all the mines for some miles around, though, in fact
each group of mines or hills has been given a separate name, but as
these so-called districts are mostly without organization, all the
claims and mines will be considered under one head.
The geology of the district about Oro Grande is complex, the formations
being uplifted, greatly faulted, and broken, besides the intrusion of
dikes of felsitic rock, diorite, and quartz porphyry. I had not
sufficient time at my disposal when at Oro Grande to study out the
somewhat intricate geological problem, and will describe the region in
general terms.
Commencing at the town of Oro Grande, which stands on the bank of the
Mojave River, the country rises in a gentle slope toward the hill half a
mile distant; gently rolling hills are reached, which in turn give place
to more rugged masses, and finally to a rough mountainous area, the
hillsides being almost precipitous. The lowlying country about the base
of the hills is mostly made up of schistose micaceous rocks, a quartzose
mica schist predominating. The first hills of any consequence are
eruptive, mostly a light-greenish felsite and a coarse-grained
porphyritic rock. Beyond are prominent hills of a dense, hard quartzite
resting upon a crystalline limestone, the highest hills being made up of
practically the same materials (quartzite and limestone), in part
schistose with some mica schist, jasper, and many intrusive dikes of all
the previously mentioned eruptives, prominent among them being diorite
of dark-green color.
THE EMBODY MINE.
Within half a mile of the town, and on a lower spur or ridge that makes
down from the hills, is located the Embody Mine, which, during the
excitement at this locality in 1890, attracted considerable attention.
The gold-bearing material is quartzose, micaceous rock of somewhat
friable character. The deposit, as I may term it, has the appearance of
being an impregnation without definite form.
Were it not for the fact that the shoot of gold rock makes across the
strike of the schists, it would resemble some bedded deposits found at
the Homestake, Black Hills, South Dakota, where micaceous schists have
been silicified and hornblende schists metamorphosed to chloritic
schists, the whole carrying gold across a broad zone 1,600 feet in width
and 6,000 feet in length. The gold occurs in shoots or vein-like zones,
without defining lines of any character. At the Embody Mine, too, little
development has been done to make any positive prediction as to the
future of the mine. The formation strikes northeast and southwest, and
dips 70° southeast.
The country is somewhat broken up, but no considerable masses of
shattered rock were observed. The croppings are quite heavily stained
with iron oxides of brown and red shades, and this mineralization can be
traced some distance. Two shafts, one nearly 100 feet deep, the other
about 30 feet, have been sunk on the deposit, exposing rocks of uniform
character, all carrying some gold. The width of the gold-bearing zone is
undetermined, but it is thought to be from 6 to 20 feet.
As far as I learned, a “mill-run” had never been made on the rock from
this mine. Mining operations had been stopped and the property involved
in some sort of dispute. The value of the rock was given to me as $8 or
$10 per ton.
THE CARBONATE MINE.
The principal mine of this district, and the one which gave the camp its
fame, is the Carbonate Mine. It was discovered by a man named Collins,
who was working in a lime quarry near by. Collins found croppings of
ore—limonite and manganese—containing silver. He developed the property
somewhat, but it finally passed into other hands, and is now owned by a
Los Angeles company, which has opened the mine quite extensively.
The formation which incloses the vein has a general trend northeast and
southwest, the dip at the main workings being not over 20°. Here an
inclined shaft has been sunk to a depth of 225 feet on the vein. At the
bottom the shaft has attained a vertical depth of about 100 feet. Two
veins of ore, consisting principally of silicious and earthy iron oxide
and black oxide of manganese with carbonate of lime, sometimes
crystallized, extend from the surface to the bottom of the incline.
These veins are very irregular in size, varying from a mere seam to
upwards of 2 feet in places.
The value lies in the lead carbonate and silver which accompany the
gangue minerals. The two veins are curiously formed at contact with
massive blue limestone and mica schist. The schist is from 1 to 4 feet
in width, the ore lying both above and below it, the whole being
inclosed between hanging and foot walls of crystalline limestone. At
various points in the workings is a light-colored, much decomposed rock,
resembling felsite, which has the appearance of having been injected
between the strata in a thin sheet. It is a notable fact that where this
buff-colored, granular appearing rock occurs in contact with the vein an
enrichment of the ore is noticeable, and its absence is marked by the
low value of the ore or no ore at all. In this incline, at a depth of 40
feet, a short drift has been run in on ore of good grade. At 180 feet
from the collar of the shaft the discovery was made that caused this
mine, and, in fact, the entire camp, to become at once the scene of
excitement.
At this place a small wedge of crystalline, granular quartz and calcite
appeared, and with it flakes of free gold. Just below the point of this
discovery the wedge widened to several inches, and the rock was a mass
of glittering sheets and shot-like pieces of gold. Assays of the
material gave fabulous returns. The ore was broken down on canvas, and
every ounce of it sacked on the spot. This was followed down some
distance, but gradually thinned out below the 200-foot level, where
drifts were run, one 50 feet northeast, the other 40 feet southwest.
From these drifts considerable rich quartz was obtained.
In the southwest drift the formation is badly displaced and broken and
the vein is lost, a fault having thrown it, but whether up or down could
not be determined, as the adjacent rock was so badly fractured. Ore was
found at the face and along the sides of some of the cuttings, and some
free gold was found on the 200-foot level in the southwest drift. All
work on this part of the mine had been suspended some time prior to my
visit, the mine having been enjoined.
ORIGIN OF THE VEINS.
This question is one which finds its answer, it would seem, in the fact
that the sheet of mica schist included between the heavy masses of
limestone represents what at one time was possibly a bed of sandy clay
or mud, which with the metamorphosis of the region has become a
crystalline schist. The planes separating this schist and the limestone
above and that below it were evidently planes of weakness, and when the
forces which uplifted and fractured the strata exerted themselves these
rocks slipped and ground upon each other, causing considerable crushing
along these planes; possibly open crevices resulted in some portions.
Ore was subsequently deposited in these interstitial spaces, partly by
substitution of ore for limestone, no doubt, and partly by precipitation
in the crushed mass of lime and schist. The injection of a sheet of
felsite into the same plane of weakness can easily be conceived, as such
intrusive bodies always follow the lines of least resistance. The
extreme richness of the rock, together with its somewhat unusual
association of quartz and calcite, attracted no little attention to the
property at the time of its discovery.
A FISSURE VEIN.
Southwestward from the deposit just described is a vertical shaft 125
feet deep. This shaft has followed down what seems to be a fissure in
the limestone, in which lead carbonate, some galena, limonite quartz,
calcite, and manganese oxide occur. This ore was worth at Socorro, New
Mexico, $50 per ton for the gold, silver, and lead it contained, and it
was shipped there in quite large quantities.
A large stope commences on the northeast side of the shaft at a depth of
30 feet from the top and extends down to the 114-foot level.
Considerable ore was standing in sight in the mine at the time of my
visit, but nothing was being done. The company have had to stop work, as
the owners of the lime quarry claim to have this property included in
their patent.
OTHER CLAIMS.
There are scores of other claims in this interesting district, but
little development has been done on them. Here and there are encouraging
prospects, where carbonate of lead and oxide of iron have been found;
but on the most promising of these only 10-foot holes have been sunk.
The mineral zones are not well defined, and the prospectors have not the
capital necessary to systematically prospect the hills.
THE SILVER MOUNTAIN DISTRICT
Is 5 miles south of Oro Grande. There are a number of claims, the
principal one being the Amazon. The formation is similar to that about
Oro Grande. In a large dike of diorite occur the ore bodies of the
Amazon Mine, which produces copper ores of a fair grade. Several holes
were sunk to various depths, ranging from 15 to 30 feet, by the Mormons
who settled on the Mojave River years ago. Recently a shaft has been
sunk to the depth of 61 feet, and a drift run north 40 feet. The ore is
principally copper-iron sulphide (chalcopyrite).
The ore in this mine occurs along slips or fault planes. This peculiar
class of deposits has been described under the head of the Tiptop Mine,
Lava Beds District, in this county, and as the essential features of
this mine are similar to those of the Tiptop, repetition here will be
unnecessary. I found a greater mineralization of the limestone in this
district than about the Oro Grande, though no prospecting has been done
here for lead ores.
GEM MARBLE QUARRIES.
Twelve miles northeast from Victor are the Gem quarries, that produce
variegated marbles of great beauty. Shades of yellow, chocolate, black,
pale blue, crimson and gray, cream-colored, rose, and white. The
markings are such as to produce beautiful effects. The croppings are
strong, and the surface material is apparently not at all injured by the
exposure of centuries to the elements in a region where nearly all rocks
decay and disintegrate rapidly. The outcrop stands boldly above the
adjacent country rock from 10 to 20 feet. The entire ledge or belt is
made up of bands or beds ranging from 3 to 6 feet in thickness. These
strata are separated by thin seams or fractures, but it is reasonable to
presume that this separating line or joint will disappear as depth is
attained. The rock is all susceptible of a high polish, and it
withstands a tremendous crushing force. It was said by the owners that
this had been determined at 28,000 pounds per square inch.
The quantity is large, the variety abundant, and the beauty approaches
that of rare onyx. With these unusual conditions surrounding the
deposit, its marketing should become an industry of no small importance.
The difficulties of transportation are not insurmountable.
LIME AND GRANITE QUARRIES.
Near Oro Grande and Victor several lime quarries are in operation,
constantly giving employment to quite a large number of men. Lime is
burned in large kilns, which finds a ready market in Southern
California. Granite is also extensively quarried near each of these
places, and used for building material, curbing, and paving blocks in
Southern California cities. This industry employs, all told, about one
hundred men.
THE KENT MINE.
Three miles from Hinkley Station, on the Atlantic and Pacific Railroad,
between Barstow and Mojave, is located the Kent Mine, a vein covered by
two claims. A shaft 80 feet deep and some superficial development have
exposed the ore, which varies from 3 to 10 feet in width. The gangue is
a rather fine-grained, granular quartz, containing galena and lead
carbonate. Assays in gold and silver are obtainable anywhere in the
vein. The highest grade carries lead 70 per cent, gold $25, silver 24
ounces. Some of the ore assaying low in lead contains gold and silver in
paying quantities.
The property is in a prospective stage only, but is promising. Water can
be obtained near the mine, and fuel is but 8 miles distant. The owner
bonded the property in May, 1892, and it is at this writing being
developed by the prospective purchasers. The ore is of such character
that by sorting a milling ore may be obtained, the high-grade lead ore
making a very good smelting material.
THE BLACK HAWK DISTRICT.
Three years ago the Black Hawk District, 40 miles east of Victor, on the
north side of the San Bernardino range, attracted considerable attention
through the extensive operations of an English syndicate at those mines.
Development was in progress at that time, and it was planned to build a
sixty-stamp mill. The quantity of gold rock, however, proved to be
smaller than had been anticipated, and a small experimental mill was
built; but from a short time after the completion of this mill to date
all operations have been suspended, and the probability of the
resumption of work is not bright.
The gold occurred in a reddish oxide of iron in bunches and stringers
scattered through a crushed zone of limestone, lying along the flank of
the mountains. A party, who for a time was in charge of the property,
informed the writer that he had worked the rock without sorting, had
endeavored to sort it, and had tried screening it, but that
notwithstanding every precaution was taken, he had concluded that it
could not be made to pay. The gold-bearing rock was quite rich, but it
occurred in too small quantity to make it profitable.
SILVER REEF DISTRICT.
Four miles northeast of the Black Hawk Mines, lying down on the desert,
is a formation of limestone and quartzite, resting on a massive
crystalline rock, containing quartz, feldspar, biotite-mica, and
hornblende. This reef extends from the mouth of Texas Cañon out upon the
plain, sloping downward at an angle of approximately 5° for a distance
of 4 miles, where it terminates in a bluff 40 to 100 feet in height.
Along the entire eastern edge of this deposit it drops off abruptly as
though sharply eroded. At the northern end the reef is faced by a low
range of hills composed of the above-mentioned hornblende rock. From
this point it swings west and with irregular outline extends for 5 or 6
miles toward Rabbit Springs. The entire area, fully 25 square miles, is
cut by gulches varying from 20 to 150 feet or more in depth, that have
been eroded through the strata and down into the underlying crystalline
rocks. These cañons seem to have resulted from natural drainage, being
started by slight depressions in the rolling plateau of limestone. On
the extreme northern edge at one point, hills of considerable size have
been formed by the folding and tilting of the strata. The limestone has
been subjected to violent compression, as the whole area is faulted and
broken into millions of fragments.
I have examined not less than twenty mining claims on the reef and
traveled over the greater part of its area, and am sure I never saw a
single piece of limestone that would weigh 300 pounds, most of the
pieces measuring under 6 or 8 inches. Considerable masses along certain
zones have been granulated, and even pulverized. This fractured rock has
all since been loosely cemented by the infiltration of carbonate of lime
into the seams. Geologists who have examined this peculiar deposit do
not agree entirely upon its mode of formation. Some believe it to be the
result of chemical precipitation of carbonate of lime from calcareous
springs, similar to the Formation Springs in the Yellowstone Park. There
are many things about Silver Reef which would at once suggest the
probability of this mode of deposit, but I am very doubtful that such a
theory will stand a thorough investigation.
It was asserted that at one time a shaft sunk in the reef passed through
the lime deposit and into the “wash” of the desert beneath. On
investigation I found that the lime had indeed been cut through, but the
underlying rock proved to be crystalline hornblende rock in place,
though somewhat decomposed. At any rate it was not desert “wash.” Over
considerable areas the lime is underlaid by a stratum of quartzite of
variable thickness, less than a foot in some places, and again in others
10 or 12 feet. Over certain limited areas quartzite is wanting
altogether. The lime is mostly crystalline, varying in color. A small
portion is as white as snow, the greater part is gray or bluish, and
some of it black.
THE ORE DEPOSITS.
For fully 8 miles along the irregular front of the reef silver ores are
found. The ore deposits are usually discovered by the cherty masses of
silicious rock, which, being harder than the limestone, stand out from
its weathered surface in bunches and small, vein-like masses. Often in
breaking the cherty rocks, stains of copper carbonate are found, and
from such rock silver, and sometimes gold, is obtained. Numerous shafts,
cuts, and tunnels have been made on these claims, twenty or more in
number, and in every one ore of good grade has been found, although the
quantity is usually small. A shipment from a claim called No. 1 returned
129 ounces per ton in the Oro Grande mill. On assaying, 20 ounces can be
found on any of the claims, and rock of a higher grade running into the
thousands of dollars is not unknown on the reef.
The ore occurs usually as bunches, sheets, or stringers, which “roll”
more or less, but in a general way follow the stratification of the
limestone downward. These stringers are from 4 inches to 2 feet in
thickness, pinching and swelling both longitudinally and on their
extension downward. The average of the ores thus far found is probably
about $50 per ton. The mines have all been opened by the discoverers,
who are men of limited means, and no systematic exploration for larger
ore bodies has ever been made. They may exist, though there is no
surface indication that such is the case. At one claim, No. 9, I took a
large sample for 20 feet across the mineralized zone and found it to
assay 11 ounces silver with $2 in gold. This rock was taken from a
shallow cut 4 feet in width and 5 feet deep, 20 feet long.
The ore deposits occur without exception in zones of limestone that have
been crushed into small fragments, together with much very fine
material. In a few places I found in contact or close to the ores what
appeared to be a thin intrusive sheet of rock of undoubted igneous
origin. The original nature of this rock could not be determined, as it
was very much decomposed and bleached. It looked like the white porphyry
of Leadville more than anything else I could liken it to, and to a great
extent has, doubtless, been the source from which the minerals of the
ore deposits were derived. In many places the quartzite which underlies
the lime rock contains galena, lead carbonate, wulfenite, zinc-blende,
iron sulphide, copper, gold, and silver. Some of this rock contains
sufficient lead to be classed as a smelting ore.
The ores of the limestone deposits are chiefly chloride of silver and
embolite (chloro-bromide of silver), which is usually accompanied by
copper carbonate, sometimes a copper-silver sulphide, wulfenite, lead,
and iron in various forms, in a gangue of calcite and quartz, with
occasionally manganese oxide. Hornsilver in crystals has been found in
the fracture joints and in small cavities of a pure blue limestone,
taken from a shaft on one of the claims at the east edge of the
district. Pasadena, Riverside, Daggett, and Victor people are the
principal owners of claims. Timber can be obtained in the main range 5
or 6 miles back of the mines, and abundance of water can be had from the
cañons in the neighboring mountains or from Old Woman’s Springs, 2½
miles east of the principal claims on the reef.
Altogether the district is a most interesting one geologically and also
financially, as the high grade of some of the ore had induced the claim
owners to sink considerable money in the development of their mines.
THE GAVILAN MINES.
On the San Jacinto estate, which is owned by an English syndicate, are
located the old Gavilan Mines, which years ago produced from quartz
veins considerable gold, the rock being first crushed in numerous
arrastras, the beds of which, to the number of fifty or more, are still
scattered all about the neighborhood of the mines. In later years, under
American management, the quartz was hauled to a stamp mill in the
Pinacate District. At the time the rancho became the property of the
English people nothing had been done in these mines for many years.
During the past two years the old workings have been investigated and a
local company organized at Riverside to operate them under lease. At the
time of my visit some workmen were industriously engaged in taking down
the gallows frame of the hoist and making preparations to vacate the
premises, and this in the face of the report that had gone abroad that a
good-sized vein of pay rock had been uncovered at the bottom of the mine
at the depth of 180 feet. I did not see the alleged ore shoot and could
get no satisfaction from the men at work other than vague hints that
there was dissension among the Board of Directors.
The veins of the Gavilan Mines are not large, but of good grade,
occurring in a granitoid rock. Black tourmaline in a feldspathic and
quartz gangue frequently accompanies the gold-bearing rock. The Mexicans
worked a large shoot down to the water-line, and judging from the size
and number of the dumps these old workings must have been of great
extent. The Riverside people had sunk a new shaft at the extreme south
end of the mine 180 feet in depth. The entire region is cut by large
feldspathic and granitic veins, which course in every direction. These
veins are doubtless intrusive dikes of the variety of granite called
pegmatite. White scales of muscovite occur sparingly, but tourmaline is
abundant.
THE VANDERBILT DISTRICT.
Forty-five miles from Fenner, on the line of the A. & P. R. R., in the
eastern part of the county, near the Nevada State line, is the
Vanderbilt District. It lies between Palm District and Ivanpah, at an
elevation of 6,000 feet above the sea. Numerous claims have been located
on the veins of the district and considerable development done. Messrs.
Patton, Taggert & Hall own eight promising claims, which it is their
purpose to develop extensively. A shaft 4½ by 6½ feet has been sunk on
the vein to a depth of 60 feet, besides which a number of shafts of
lesser depth and numerous open cuts have been made, all exposing ore of
good grade. The vein is of the branching kind. The veins vary from 5 to
30 feet in width, striking east and west, with a dip to the north of
60°. The gangue is quartz, honey-combed at the surface from the
oxidation of the sulphurets it originally contained, small disseminated
crystals of which (iron, lead, and copper) begin to show in the rock
from the deepest parts of the workings. Some of the rock contains a high
percentage of lead in the form of galena and carbonate, but it occurs
mostly in bunches and is not evenly distributed through the rock. A
shipment of 6,963 pounds to the sampling works at Kingman, Arizona,
returned an average assay value of $173 50 per ton, most of which was
gold. Another lot averaged $44.
Near the above described property Messrs. Simmons & Roberts have sunk
three shafts to a depth of 40 feet each, and Campbell & Beatty put down
a shaft 100 feet, all in ore of a character and value similar to that
found in the other mines. Both wood and water are obtainable in the
district, pine timber growing on the hills, and a good stream of water
is flowing down into the desert only 1¼ miles distant from these mines.
With the character and grade of the ores found in these veins, and the
advantages of wood and water, it would seem that these mines might be
successfully operated, particularly as some of the owners are possessed
of sufficient means. It is the expressed intention, however, to sink
deeper and determine more fully the extent and character of the ore in
depth before placing expensive machinery on the ground.
THE IBEX MINE.
Among the mines that have attracted unusual attention in this county
during the past year, the Ibex Mine stands prominently in the front
rank. It is located 3½ miles from Ibex Station, on the line of the A. &
P. R. R., and not over 11 miles north from The Needles. The Ibex
property is in the Ibex Mining District, and consists of seven claims,
which were located in 1888, now owned by residents of Riverside and San
Bernardino. The principal claim is called the Ibex. The vein strikes
east and west, dipping at an angle of 45°. Two shafts, one 60 feet and
one 52 feet, had been sunk at the time this information was obtained. At
the bottom of the 52-foot shaft a drift 38 feet in length has been run
on the vein. Surface cuts and trenches are quite numerous on the several
claims, and a large amount of quartz containing gold had been exposed.
Free gold could be seen in considerable quantity in some of the porous
quartz. The quartz is thoroughly crystalline, showing many cavities as a
result of the decomposition and leaching out of the sulphuretted
minerals it originally contained. These cavities are all lined with
minute quartz crystals, which have been deposited evidently since the
removal of the sulphides. Rock of this description is full of gold,
seemingly. It is so loose in texture that careless handling shakes out
the golden grains. John Anderson, of San Bernardino, one of the owners,
volunteered the information that from 2 to 4 feet of this rock sampled
$100 to $150 per ton. The owners had determined the latter part of April
to ship this free-milling ore to The Needles, where a mill was being
constructed. Some of the quartz from the lowest workings contains small
crystals of pyrite and chalcopyrite, but it would still be classed as an
ore susceptible of free amalgamation. The Ibex property had a promising
look in the spring of 1892. Its further development will be looked to
with great interest by all interested in desert mines.
MONTE NEGRAS DISTRICT.
Near the south boundary of San Bernardino County, and about 75 miles
directly east of Mount San Bernardino, a new mining district has been
organized within the past two years, and considerable development work
accomplished by the claim owners, who, as usual, are men of limited
means.
This district is 22 miles northeast of Cottonwood Springs, 16 miles
north of Eagle Mountain, and about 6 miles south from Virginia Dale. The
belt is about 1½ miles in width and 5 miles in length. The veins trend
north and south.
This new district, which has been named the Monte Negras, or Black
Mountain District, has attracted considerable attention by the discovery
in one of the claims of nuggets of gold and quartz of extreme richness.
At the time of this discovery some newspapers in this county published
the report that the mythical “Pegleg Smith” Mine had actually been
found, which only added to the excitement produced by the bringing into
San Bernardino of several hundred dollars worth of specimens.
I visited this new district in the month of May, 1892, and spent several
days in making an examination of the claims and adjacent country. The
Monte Negras camp is on the south side of the range of hills 45 miles
northeast of Walters Station, on the line of the Southern Pacific
Railroad, being reached by a fair desert road. By fair I mean a heavy,
but not rough or hilly road.
Walters Station is nearly 200 feet below the level of the sea. From that
point every foot of the way is up hill, till a divide near Cottonwood
Springs is reached, at an altitude of 3,157 feet, the distance being 27
miles; from there to the foot of the wash, which extends 2 or 3 miles
from the base of the mountains, down hill 19 miles, where the altitude
is 1,300 feet. The altitude of the camp is 1,520 feet. All the mines
lying back in the mountains are at higher, though varying, altitudes,
the greatest elevation being 3,500 feet, at the Ramona. The neighboring
peaks rise from 200 to 800 feet higher.
This district is distant about 35 miles from Cadiz, on the line of the
Atlantic and Pacific Railroad. I have never traveled the road, and know
nothing of it, although I am told it is a good desert road. Wood is not
obtainable at all in the vicinity of the mines, and water is scarce, but
has been obtained by sinking a well in a basin at Virginia Dale, a few
miles north of these mines. A shaft was sunk 140 feet in the wash 3
miles south of the most southerly Monte Negras mines, but no water was
obtained. Bedrock was not reached at the depth mentioned, but it is not
unlikely water may be secured by continuing this shaft downward.
I mention all these drawbacks to what I otherwise believe to be
promising property, because I think the difficulties may be offset by
the fact that the ore is high grade.
The Monte Negras uplift consists, as far as my observation extended,
entirely of eruptive rocks, diorite, quartz porphyry, and fine-grained
more or less porphyritic rocks, cut by later dikes of felsite and
dark-green or black diorite. Epidote occurs in great quantity throughout
the region, usually associated with micaceous iron ore, which is found
in the form of veins and bunches everywhere. The iron ores contain no
precious metals, and are of no economic importance.
The region, although entirely eruptive, and in part volcanic (large
fields of basalt occurring on the western slopes) is in the immediate
vicinity of a large hill called Pinto, or Painted Mountain, which is
made up of metamorphic strata, chloritic and hornblende rocks, quartzite
and mica schist predominating.
The mineral-bearing veins of the Monte Negras District are all of the
fissure type, and are mostly quite simple in form. The gangue is quartz,
carrying iron and copper sulphurets, and the secondary products of those
minerals, iron oxide and copper carbonate, with gold and silver. No lead
or zinc was observed. The economic value of the ore lies almost,
evidently, in its gold contents, the silver occurring so sparingly as to
amount to very little. The bullion obtained from these ores is worth
about $17 per ounce. The ore ranges in value from $20 to over $100 per
ton. Observations on the principal mines of this district, viz.: Great
Eastern, Venus, Columbus, Summit, Porcupine, Schiller, Hillerman, Annie
Rooney, Ethel, Republican, Ramona, McKinley Bill, and Revenue, have to
be omitted in order to condense the report.
SAN DIEGO COUNTY.
By W. H. Storms, Assistant in the Field.
There has been no marked development of mines in this county since the
last report was issued, excepting in some of the districts of the
Colorado Desert, of which mention will be made. The general geological
and topographical features of this county have been so fully described
in former reports that to repeat them here is unnecessary. At various
times within the past two years new discoveries have been announced, and
these have been developed to a greater or less extent, and in some
instances, at least, with encouraging results.
HELVETIA MINE.
This mine is located a short distance from the town of Julian, and is
equipped with a steam hoist and mill combined under one roof. The new
shaft, which was started nearly three years ago, was sunk on the vein
for 50 feet, at an angle of 75°, at which depth the shaft left the
crevice and continued vertically to a depth of 225 feet. From this point
a crosscut was started back toward the vein, running at an angle with
its strike, the idea being to reach a pay shoot as quickly as possible.
The shoot in question was the south extension of that developed in the
old workings. The vein was encountered, and the drift continued along
its course. At about 30 feet from the point of intersecting the vein in
this drift of the shoot was found. It was hard, blue, rather
glassy-looking quartz, filled with minute black particles, and showing
considerable gold, some of the rock being very high grade.
The drift was continued along the vein, and finally reached a point over
the level that had been run south from the old shaft, which is 300 feet
deep. This new drift was found to be 14 feet higher than the old level.
The mine was completely drained at the time of my visit, and a free
circulation of pure air was found throughout the workings. The ground
was ready for stoping, but owing to some legal difficulties arising the
property was lying idle.
The appended sketch will give an idea of the present development of the
Helvetia, which is one of the most promising properties in the district,
and a type of the best class of mines of its kind found there.
The Helvetia, like other mines of the district, occurs in the
crystalline schists, the quartz being found as lenses inclosed in the
country rock. Some of the lenses might be mistaken for fissures, but I
failed to see one possessing the characteristics of a “fissure.”
Nearly all the lenses exhibit a tendency to “make” into the hanging wall
side of the country rock, the lenses of quartz following each other in a
general direction, but at an angle with the stratification of the
schists, and are separate and distinct from each other, being separated
at the ends (where they sometimes overlap) by the “leaves,” as they may
be termed, of the schistose country rock. These lenses were doubtless
caused by a compressive stress on the schists, which had a tendency to
split them, but was not powerful enough to cause an abrupt fracture. The
accompanying sketch may convey an idea of the occurrence of these quartz
lenses.
[Illustration: _WORKINGS OF THE HELVETIA MINE NEAR JULIAN_]
[Illustration: _LENTICULAR QUARTZ BODIES IN SCHISTOSE ROCK_]
By the above sketch it will be observed that there is a tendency on the
part of the quartz lenses to follow a given direction, which lies at a
small angle across the strike of the schists, and that these lenses are
not connected, but occur independently, though all are the result of the
same force which flexed and split the strata.
Other mines about Julian were idle at the time of my visit, the most of
them being inaccessible, owing to water in the workings. Considerable
money has been expended on the Owens Mine in an attempt to drain and
recover the workings, but it was abandoned after several months of work
and considerable expense.
More activity was exhibited in the mines about Banner than any other
part of the district.
READY RELIEF MINE.
This is the largest and most extensively developed mine near Banner. It
has earned considerable fame, not only as a producer, but for the
peculiarities exhibited in the formation of its bunches of quartz, which
contain disseminated grains and masses of pyrite.
The Ready Relief has several levels, all of which are connected by
winzes and shafts. The huge bunches of quartz have, from their peculiar
form, been denominated “rolls,” and I know of no better term which would
convey a clear idea of their appearance. As a result of close
observation made at numerous points in the mine and on the surface at
the time of my visit, I formed the conclusion that the “rolls” of the
Ready Relief Mine simply represent an exaggerated condition of the same
sort of flexing of the schists that has produced the other mines of this
district. The facts as observed lead me to the belief that the “rolls”
or folds of the Ready Relief Mine, and its extensions, both north and
south, are the result of a severe compressive stress upon the schists at
right angle to a line running nearly northwest and southeast; that this
force was exerted in the form of pressure and not of contraction; that
as a result of this pressure there is a tendency exhibited on the part
of the contorted strata to form a reverse fault and not a normal one,
and that this power expended itself before the rocks were forced to
yield to the strain to the extent of fracture, the result being an
abrupt crumpling of the schists without disruption.
Along this line of disturbance percolating waters have deposited silica
in enormous quantities. The schistose folded masses having been
completely metamorphosed, massive quartz replacing the crushed and
crumpled crystalline rocks, though the lines of its former schistose
structure are in many places preserved.
A sketch of a characteristic section is here reproduced, and it may help
the reader to form some conception of this unusual occurrence of
gold-bearing quartz. The strike of the country rock is about northwest
and southeast, and varies but little from this over a wide area. The
rock is, generally speaking, a dark gray, rather close-grained,
micaceous rock (argillite), having a dip to the east of about 80°. The
succession of folds cut across the dip of the schists at an angle about
45° from the horizon.
It will be noticed that in places several of the rolls lie side by side.
Where this occurs the pay shoot is very large. The thickness of the
individual rolls varies from a few inches to 5 or 6 feet, and where the
folds parallel each other a width of 12 to 20 feet or more is not
uncommon. These rolls do not extend longitudinally a great distance, but
seem to gradually diminish, being followed by others along the strike of
the vein. It seems quite evident that had the stress which produced this
folding or crumpling of the schists proceeded much farther an abrupt
fracture must have resulted, and the Ready Relief vein would have been a
fissure having a dip of about 45°.
At the time of my visit the Bailey Bros. were overhauling their mill of
ten stamps and were putting in a 12-foot waterwheel of the Pelton style.
Though large amounts of quartz have been stoped from the Ready Relief
there were still thousands of tons in the mine. Mr. Bailey informed the
writer that the rock averaged about $15 per ton.
The other claims which occur along the same course as the Ready Relief
are quite similar from a geological standpoint, though none of them
exhibit the peculiarities of the folds in such a marked degree. Among
the prominent mines on this belt are the Hubbard claims, which were
being operated in the spring of 1892, the Redman, Antelope, Cincinnati
Belle, and some others.
THE RUBY MINE.
This mine is located a short distance east of and parallel with the
Ready Relief. It occurs at the contact of mica schist and syenite. A new
five-stamp mill was in course of construction at the time of my visit,
in which it was intended to crush quartz from the Ruby and Wilcox, an
adjoining location. A small force was employed at the mine.
THE KENTUCK S.
Since the last report was published the Kentuck S came into prominence
once more under the ownership of a St. Louis syndicate. A vigorous
policy was inaugurated, and for a time all seemingly went well. The
shoot of quartz, which had been opened to some depth, crops out along
the flank of the steep mountain side. The vein pitches into the hill at
a high angle. The manager selected a place to start a new vertical,
three-compartment shaft at a point up the hill about 100 feet above the
croppings. The shaft was started and was fully equipped. Massive timbers
were placed in the most approved style. At a depth of 100 feet the work
has reached the level of the croppings, and had cost, it is said,
$10,000, and it was still about 125 feet down to a connection with the
vein. Here the work was stopped, and has never since been resumed,
standing an excellent example of how not to open a mine. The money
expended in this shaft would have driven a crosscut tunnel from the base
of the hill to the vein, giving at least 500 feet of backs, affording a
cheap means of draining, ventilating, and exploiting the mine.
CINCINNATI BELLE.
Among the most promising properties I saw about Banner is the Cincinnati
Belle, which has made quite a record as a producer of rock of high
grade. This mine, together with several other claims, was purchased by a
Pomona company in 1890, for the purpose of operating these mines, among
them being the Gold King and Gold Queen Mines, of which mention will be
made hereafter. The Cincinnati Belle is situated about 3,000 feet
northwest from the town of Banner, and is in charge of D. C. Lane.
The shoots or lenses of quartz which constitute the so-called ore bodies
of this mine occur in a general course along the strike of the schists,
though each succeeding lens to the northeast “makes” into the hanging
wall, as indicated in the cut under the head of Helvetia Mine.
The mine was developed by a tunnel of 168 feet in length, of which the
first 40 feet required timbering. Near the mouth of the tunnel a shaft
has been sunk on the pitch of the quartz lenses, to a depth of 200 feet.
Levels were opened at intervals of 50 feet. The first level at the top
had been cut 168 feet along the course of the lead; the second 68 feet;
the third 120 feet; the fourth, fifth, and sixth each 50 feet. Each
level exposed a bluish quartz rock, which returns in the mill from $18
to $40 per ton. It is free milling, and is treated by a simple
amalgamation process.
Though this quartz contains some pyrite, which is auriferous, carrying
$8 to $10 per ton, no attempt is made to save the sulphide. The mine
makes but little water, and all the quartz and waste are hoisted in a
bucket. Pine timber is used, which grows in the neighboring mountains
above the mine. It costs 11 cents per running foot at the mine. The
property was only under process of development at the time of my
examination, and as but little stoping has been done, the cost of mining
per ton could not be arrived at. The lenses vary greatly in size,
ranging from a few inches to 4 feet. The vein or mineral-bearing zone is
accompanied by a fissure, which runs along nearly parallel with the
quartz at a distance of a few feet on the hanging wall side. This fault
has resulted in the crushing of the country rock along its course.
In this vein, as it may be called, the rock has been completely changed,
clay, talcose, and chloritic mineral replacing the micaceous rock. This
mineral contains some gold. The inclined shaft has two compartments and
is substantially timbered throughout. From the mine the company has
graded, along the mountain side, 4,000 feet of road, over which the
quartz is transported to the mill in the town of Banner at an expense of
75 cents per ton. The mill contains ten stamps.
The mill is quite complete, but poor judgment was shown in the
arrangement by the management under whose supervision it was built,
which was before the present Superintendent was in charge. As an
instance, the rock from the mine when delivered at the mill is dumped
into an ore bin outside the mill. The rock is then taken inside as
required and dumped on a grizzly. As usual the large pieces fall on the
crusher floor, where they are fed by hand into the jaw rock-breaker,
which stands above the level of the floor. This sort of management
necessitates extra and unnecessary work.
THE GOLD KING AND GOLD QUEEN MINES
Are located about 4 miles west from Banner, and are owned by the Pomona
company, that owns the Cincinnati Belle. Only four men were employed in
these mines at the time of my visit, prospecting work only being done.
The quartz raised from these workings is hauled 11 miles by road to
Banner. The quartz is high grade, and pays well, but no large amount was
developed.
THE STONEWALL MINE
Is located about 8 miles southwest from Banner on the Cuyamaca grant,
belonging to the Waterman estate. The Superintendent, Waldo S. Waterman,
informed the writer that nothing of special interest had been developed
in the mine since the publication of the last report (1890).
MESA GRANDE DISTRICT.
A few miles to the northwest from Julian is located the Mesa Grande
District, where lenses of a yellowish pellucid quartz of semi-granular
texture have been developed somewhat. All of this quartz contains gold,
and some of it is quite rich; but nothing of consequence has been done
of late, further than to organize a stock company.
ESCONDIDO MINES.
Near the flourishing little town of Escondido are some old Mexican
mines, which have been acquired by a San Diego company. The veins are
gold-bearing, the quartz having formerly been worked in arrastras with
evidently good results, as the surface workings are quite extensive.
Within the past two years, however, little has been done on the
property.
PINE VALLEY.
The Pine Valley Mines lie 6 miles from the Stonewall and San Diego Stage
road, the nearest station being Descanso. Two mills, one of five and one
of two stamps, crush the rock taken from the veins in the vicinity. This
quartz, it was claimed, would mill over $50 per ton. The veins occur in
a formation similar to that about Julian and Banner.
REPORTED TIN DISCOVERIES.
Frequently there have been rumors of the discovery of tin stone in San
Diego County, but up to this time no such ores are known to exist
outside of the property known as the Temescal Mines, which are located
on the line of San Bernardino and San Diego Counties. However, in the
large crystalline area which extends over a considerable portion of San
Diego County, it would not be strange to find tin stone under conditions
similar to those which obtain in the Harney Peak region in the Black
Hills of Dakota. There the cassiterite is found in good-sized crystals
and finely disseminated grains in a matrix of coarse-grained granite,
which has been thrust up through the schists in the form of intrusive
dikes of greater or less size. It usually is associated with tourmaline,
wolfram, and other black minerals, making it difficult to distinguish it
without making a test of some sort. The search for tin in San Diego
County has been confined to looking for a black rock similar to that
found in the Cajalco Mine.
DULZURA DISTRICT.
The Dulzura Mining District is 30 miles east and a little south of the
city of San Diego, in a range of rather rugged mountains. Metamorphic
rocks occur frequently, but masses of igneous rock have been intruded
and constitute large hills throughout the district. Among these rocks
are a light, greenish-gray feldspar porphyry, a dark-green, fine-grained
diorite, a black aphanitic diorite, sometimes porphyritic, and a light
cream-colored or greenish-white felsitic rock. In the immediate vicinity
of Dulzura the latter rock occurs in the form of immense dikes striking
northwest and southeast, crossing Cottonwood Creek to the south into
Mexico. In one of these great dikes, which is several hundred feet in
width, the mines of the district are found. They are principally
chambered veins occurring on the line of a fault plane which has
fractured the felsite, the hanging wall side of the slip going down, the
movement causing the rock to become crushed and broken. Percolating
waters have carried into the crushed mass mineral solutions, which have
deposited the ores, chiefly iron sulphurets, where the most favorable
conditions were found along the line of this fault plane. The subsequent
oxidizing of the masses of ore thus formed has stained the rock a bright
or dark red and sometimes yellow.
The rock contains gold ranging from a trace to $20 or over per ton. It
was said the average was about $8. The oxidation of the ore bodies does
not extend to any very great depth, the result being the occurrence of
sulphuretted ores comparatively near the surface, though it was claimed
by the mine owners that the sulphurets contained sufficient gold to make
concentration and treatment by chlorination profitable. The mines are
quite interesting from a geological point of view, and may, in time,
prove equally so from a financial standpoint. No machinery had been
built at the time of my visit. The felsite throughout the district,
whenever observed, contained a considerable amount of pyrite, the
surface rock nearly always presenting a highly mineralized appearance.
JAMUL CEMENT ROCKS.
The Jamul Portland Cement Mine and works are located on the Jamul
rancho, 22 miles east of the city of San Diego. The company began the
construction of expensive works in the spring of 1890, which were not
completed until June, 1891, at a cost of $50,000. Seven kilns were
constructed, together with large buildings. The capacity of the works is
about 150 barrels a day. When in operation over forty men are employed
at the mine and works.
The transportation problem proved a more serious one than had been
anticipated, it costing more to haul cement from Jamul to San Diego than
it costs to bring English Portland cement to California by vessel. The
cement made by this company has been quite extensively used throughout
Southern California.
ASBESTOS.
The John D. Hoff Asbestos Company, of San Diego, is operating an
asbestos mine in the San Jacinto Mountains, from the product of which a
variety of fire-proof material is made, including roof paints, roofing,
boiler and steam-pipe covering, fire-clay goods, etc. This is the only
asbestos concern in the southern part of the State, and the business
seems to be on the increase. The works are located near Pacific Beach, 7
miles from San Diego. Asbestos is also found near Palm Springs, in the
San Jacinto Mountains, and several miles east of Indio.
PINACATE DISTRICT.
Near the line of San Bernardino and San Diego Counties, about 5 to 8
miles west from the town of Perris, are the mines of the Pinacate
District, all being veins of quartz-bearing gold. In past years this
district has produced a large amount of bullion, the quartz being worked
in arrastras, the beds of over a hundred of which still may be seen
scattered about.
There are numerous springs of small size in the district, but timber is
very scarce. The formation is syenite and granite principally;
occasionally schistose and gneissoid rocks and quartzites being
observed. The entire region is metamorphic, excepting a few dikes of
granite (pegmatite) and quartz porphyry. Diorite is found near the Good
Hope Mine. The region is one easily accessible, and but 4 to 8 miles
from a railroad.
STEELE’S MINE.
To the northwest of the Good Hope Mine is the Victor Mine, formerly “La
Plomo.” This mine is now better known as the Steele Mine. The vein is a
foot or more in width, consisting of a highly crystalline quartz, in
which is disseminated a small amount of iron and lead sulphuret and lead
carbonate. The rock is quite rich in gold, some of it showing gold
without the aid of a lens.
A tunnel 900 feet in length had been run to develop the vein, on which
an inclined shaft had been sunk to a depth of 200 feet. Besides this
work there were numerous other superficial workings, in which quartz of
good grade was exposed. The vein occurs in a region of metamorphic
rocks, the foot wall containing much quartz and biotite mica. The
hanging wall is dark gray color, and quite fine-grained in texture.
Hornblende crystals are plentiful throughout the rock. Other rocks in
the vicinity are mica schist, chloritic rocks, quartzite, and other more
massive crystalline rocks. Granitic dikes (pegmatite) cut the formation
on all sides, none of them being very large. These dikes are
characterized by their exceptionally coarse crystallization. Good-sized
tourmalines, of jet black color, are numerous in the granite.
THE ROSALIA.
About a mile northwest from the Victor is the Old Rosalia, now the Santa
Rosa, which is opened along the surface for over 1,000 feet by cuts and
shafts. The upper portion of the vein was worked out years ago, but new
capital has been interested and a new shaft was being sunk at the north
end of the property.
The inclosing rock on either side of the vein is very soft and much
decomposed, requiring more timber than had ever been used by the former
operators. The mine has produced a large amount of gold, which was
extracted by working the quartz in arrastras, and in later years in a
mill, which still stands on the mine. At the north end it was understood
that the shoot of pay rock was still intact, and it is to recover this
that the new work was being inaugurated. The balance of the shoot to the
south has all been worked out down to the water-line.
THE SANTA FE.
Not over half a mile from the Rosalia is the old Santa Fe Mine, which in
days gone by was a producer of gold, but its workings had long been
abandoned.
THE SHAY MINE
Is also in the Pinacate District, 6 miles west of Perris. Several holes
have been sunk on the vein, but the entire lower portion of the mine was
flooded and could not be examined. The quartz is a bluish, ribbon-like
rock, and carries considerable gold. The owner from lack of means is
unable to work the mine.
There are numerous other mines or veins in the district, many of which
have been worked in former years by Mexicans, who coyoted about, working
the narrow seams and crushing the quartz in arrastras. These veins are
now abandoned, and no one seems to have sufficient faith in their value
to undertake anything like systematic development. The veins mostly lie
quite flat in granite or syenitic rocks. They are usually from 4 to 16
inches in thickness and extend some distance. Roads are constructed to
nearly all of them. It seems like a region promising good returns on
small investments. One ten-stamp custom mill could crush the rock for
all the veins of this district. I was informed that much of the rock
returned from $60 to over $100 per ton.
THE MENIFEE MINE
Is located south of Perris about 8 miles. The vein contains gold-bearing
quartz. The foot wall is a chloritic schist, back of which lies a
syenitic rock. The hanging wall is syenitic granite, the hornblende
having changed partly to chlorite. The vein is from 1 foot to 30 inches
in width, and strikes northeast and southwest, dipping west 80° to a
depth of 40 feet, where it flattens out to 65°. The quartz mills about
$15 per ton, and contains but a small percentage of sulphurets. There
are four shafts on the vein, varying from 35 to 60 feet in depth, the
main shaft having a double compartment, being 5 by 11 feet. They have a
five-stamp mill.
THE WALKER CLAIM.
Within a mile of the Menifee, in a northeasterly direction, a new
discovery was made in the spring of 1892 of a quartz vein which occurs
on a low mound at the base of low, rolling hills. The vein was small, 4
inches to a foot, quite heavily mineralized, but much broken. Two
distinct faults occurred in a length of 90 feet, where the vein had been
exposed. Two shafts were down 30 feet each, and water was coming in. The
finding of specimen rock had created quite an excitement in the
vicinity, and visitors were numerous. The rock, I judged, would pan out
about $40, but too small an amount of work had been accomplished to make
any estimate of the value of the vein possible.
CARGO MUCHACHO MINE.
In the Cargo Muchacho District, 30 miles in a northerly direction from
Yuma, the Cargo Muchacho Mine has again been in operation within the
past two years. The owners moved the mill from the Paymaster Mine to a
site near the former property, laid a double pipe-line 14 miles from the
Colorado River, and have supplied the camp with water in this manner.
The latest reports from the district are to the effect that the mill and
mine are being operated steadily, with satisfactory results.
THE PASADENA MINE.
About one mile north from the Cargo Muchacho is a vein on which several
locations have been made. Of these the Pasadena and Peterson claims are
most prominent. The vein covered by the locations has been quite
extensively opened, and possesses many of the features of the Cargo
Muchacho.
The quartz was sent, at no small expense, to a mill at El Rio, on the
Colorado River. The expense of mining was seldom less than $2 a ton;
transportation to the S. P. R. R. at Ogilby Station, 6 miles, $2 50;
transportation by rail to El Rio, 14 miles, 50 cents a ton, making at
least $5 a ton. The mill was leased at $10 per day, to which the expense
of milling was added, making fully $4 a ton more, or about $9 in all. It
was claimed that the rock averaged $16. Doubtless some of it did, but it
is probable the expense really exceeded the figures given.
With water pumped into the district it is quite possible that this mine,
and the Peterson claim adjoining, may be operated at a profit, which
under former conditions was impossible. There are many other
gold-bearing veins in the region, but none of them are extensively
developed.
EAGLE MOUNTAIN.
Unusual activity has characterized operations about that portion of the
Colorado Desert, about 90 miles east of the San Bernardino Mountain,
near the line between San Diego and San Bernardino Counties. The Eagle
Mountain District is one of these localities. The discovery of rich
placers in the dry gulches of that section resulted in a more thorough
investigation of its mineral resources and in the finding of some very
rich gold-bearing quartz. Considerable work has been done on these
claims and the prospects are considered very flattering.
A cemented basin has been constructed to catch the rain water that falls
during the winter season, with which it is intended to work the placer
mines. The discoverers of these mines, it is said, took enough gold from
the gulches, in making the basin referred to, with a dry washer, to pay
for making and cementing the basin.
COTTONWOOD SPRINGS.
Twenty-six miles in a northeast direction from Walters Station, on the
line of the S. P. R. R., at an altitude of 3,004 feet, is Cottonwood
Springs. A range of mountains, in which occur granitic and metamorphic
rocks and eruptive dikes, strikes east and west across the desert, and
in these occur several springs. There is but one mine in the immediate
vicinity of the springs, and this is known as
THE COYOTE MINE,
Where a reading of the aneroid indicated 3,300 feet. The formation in
which the Coyote vein has formed is micaceous and hornblende schist and
gneissoid rock; hornblende granite and dikes of diorite also occur in
the vicinity of the vein. The Coyote Mine is a quartz vein from 2 to 4
feet in width. The rock is iron stained and occasionally shows free
gold. The vein is developed by two shafts, one about 20 and the other
nearly 80 feet in depth, and strikes 5° north of east, having a dip of
46° to the south. The vein appeared to cut the formation at a small
angle. A fault, which has occurred within the vein, had evidently
puzzled the owners, as at the bottom of the 20-foot shaft they had
developed 8 feet of what looked like solid quartz. The vein is really
but 4 feet in width at that point, but the fault cutting downward at an
angle of 45° and crossing the strike of the vein at an angle of 27° had
allowed the hanging wall side of the fault to slip downward, thus
doubling the width of quartz, which was much shattered. The miners had
quit work, leaving what they considered well enough alone. In the deeper
shaft the fault had carried the hanging wall down and to the east a few
feet, and the vein was lost altogether. A short drift had been run into
the hanging wall, but not finding the vein, work had been suspended. The
vein lies on the foot wall side and not more than 4 or 5 feet from the
line of the slip.
[Illustration: _FAULT OF COYOTE MINE
COTTONWOOD SPRINGS_]
SALTON LAKE.
By E. B. Preston, E.M., Assistant in the Field.
The Coahuila Valley, in which Salton Lake is situated, is 90 miles long
and from 10 to 30 wide. It separates the San Bernardino range of
mountains from the San Jacinto, and forms a part of the great Colorado
Desert in San Diego County. In its deepest portions it is 275 feet below
the level of the sea; the area of the depressed region is over 1,600
square miles. In its northern portion the valley consists of sandhills
and dunes, the former caused by the accumulation of the sand around the
scrub and bushes growing in the desert. The southern portion is bare
clay. On the borders of the desert palm trees of the fan palm variety
occur in a few scattered clusters. The Southern Pacific Railroad passes
through the valley on its way to Yuma.
In that part of the depression adjacent to the railroad station of
Salton is a salt marsh, where the New Liverpool Salt Company’s works are
located, and where a fine quality of table salt is produced, containing,
according to an analysis made by Thomas Price, of San Francisco:
Chloride of sodium 94.68 per cent.
Calcium sulphate .77 per cent.
Magnesium sulphate 3.12 per cent.
Sodium sulphate .68 per cent.
Water .75 per cent.
100.00 per cent.
The brine from which the salt is obtained shows a density of 27° Baumé.
The company’s works are situated about 3,000 feet west of the railroad
track, and consist of the salt mill and a large storehouse, connected by
track with the main line. This branch line extends into the marsh a
distance of over 10,000 feet. Beyond the end of the track a borehole was
sunk by the company, with the expectation of obtaining water, to a depth
of 300 feet, when the work was interrupted.
The strata passed through during the sinking throw some light on the
past condition of the desert depression, as well as furnishing some
points that may have a bearing on the flooding of this section.
The top covering consists of 6 inches of black mud, resting on a crust
of chlorides of sodium and magnesium, 7 inches in thickness. The drill
on passing through this crust dropped through 22 feet of a black ooze,
containing over 50 per cent of water. Tests of the ooze made at the
State Mining Bureau laboratory showed it to consist largely of chlorides
and carbonates of sodium and magnesium, the soda salts predominating,
besides fine sand, iron oxide, and clay, and a small amount of organic
matter. The ooze was resting on a hard clay bottom, through which the
drill passed for the entire remaining distance, only varied by two or
three streaks of cement. From the shore line of the marsh toward the
adjacent mountain ranges, the soil consists of a fine sand, containing
clay and a notable quantity of mica, and is strewn with well-preserved
shells of _Planorbis ammon_, Gould, _Physa humerosa_, Gould, and
_Amnicola protea_, Gould.
In a few spots near the northwest end of the marsh the accumulated cases
of a species of Caddice worm are found. Northeast of the marsh the
surface slopes gradually upward to where the remains of an ancient sea
beach are to be seen, stretching to the south and east to where the
Colorado River cuts through on its way to the Gulf of California.
Behind the beach extends a mesa to the foot of the San Bernardino range.
Across this mesa are evidences of heavy floods coming down the cañons of
the back range, carrying large quantities of debris with them, mostly
bowlders of mica schists and granitoid rocks, with some quartz
intermixed. On the west side of the marsh the surface has but little
elevation until the granitic bluffs of the San Jacinto range are
reached. These bluffs are coated for a distance of about 25 feet above
the plain with a sponge-shaped incrustation from 2 to 3 inches thick,
consisting largely of carbonate of lime, chloride of sodium, sand, clay,
and oxide of iron; under the glass some of the pores are seen to contain
minute shells of the same varieties as found on the sand of the plain.
Where arroyos have been cut through the sands of the plains to the depth
of several feet, the exposed sections show a stratified arrangement of
the sand, having between the layers a thin division of the same
varieties of shells as found on the surface, the whole resting on a firm
clay bottom. From the position and regularity, as well as the quantity
of these shells, on top of the different strata of sand, while but few
are seen scattered through the sand layers, a periodicity of the
conditions favorable to their existence and growth, as well as a
comparatively sudden cessation of the same, must be inferred. These
conditions mean an occasional flooding of the depression for a period of
time, during which a shallow body of water was maintained, which
evaporated as soon as the water supply was shut off. In what manner this
can occur will be shown later on. The plain supports a scant growth of
desert shrubs, with some mesquite bushes in the vicinity of the few
springs that are found scattered over the desert, most of which are
saline. The presence of the extensive line of sea beach proves that at
some time the gulf has extended much farther inland than at present,
covering the whole of this depression. The Colorado River, in its course
south to the ocean, built up a flood plain on a higher level that
finally shut off the western part from a direct communication with the
sea, and evaporation, with a gradual uplifting of this whole section,
finally laid it bare, although leaving a great part of it still below
the present sea-level. Under these conditions, whenever more water comes
down the river than its banks can contain, the silt-formed shores give
way to the increased pressure and permit the excess of water to flow to,
and gather in, what is termed the river swamp at the back of the flood
plain, from whence it either re-enters the river lower down in its
course, or finds its way into the depression.
The Salton Marsh at present acts as the catchment basin for the waters
draining from the east side of the San Jacinto range, Carizoo Creek, and
a part of the San Bernardino Mountain range, and in times of extreme
high waters as a reservoir for the excess in the Colorado River. In the
month of June, 1891, a steady flow of water entered the depression from
the southeast and continued to the northwest uninterruptedly until an
area 30 miles long and averaging 10 miles in width was covered to a
depth of 6 feet, measured at the end of the Salton Salt Works branch
track. When first examined the water showed a density of 7° Baumé, which
gradually increased to 25° Baumé. The mother liquor used in making salt
at the New Liverpool works usually shows a density of 27° Baumé. This
salt water gave rise to the idea that the waters from the gulf had made
an inroad through some underground channel, and to prove the source and
possible permanency of these waters several investigating parties were
sent out. No such previous incursion had been witnessed by the settlers,
but inquiry proved that a similar lake existed here in 1849. Finally one
of the parties showed that the Colorado River was the source, and then
the question was brought to the attention of the State Mining Bureau to
investigate as to the probability of the permanency of the lake and its
probable effect on the climate of the surrounding country.
The Colorado in its great length accumulates a large amount of sediment,
from 0.1 to 0.4 per cent per gallon, and after this has been deposited
the water on evaporation is found to contain 0.14 grammes solid residue,
consisting largely of sulphate of soda and chloride of sodium. With the
sediment the river is all the time building up its flood plain, and it
may not be out of place to recall the general laws that govern the
actions of streams while depositing the solid matter they carry in
suspension.
Currents bearing sediments deposit a large percentage as soon as their
velocity is checked in the least, but pick up deposited sediments again
as soon as the current is increased. Thus a variable current is
depositing at one point while eroding deposits at other points.
The velocity of a river current varies with the seasons on account of
the different volumes of water carried, but it also varies at different
points of the river, during the different hours of the day, through the
constant action of the laws of erosion and deposition. The banks not
furnishing a constant, even resistance, erode in the looser parts,
causing each time a deflection of the current, as well as a change in
the velocity. This action soon changes a straight stream with an even
current, to a serpentine course with currents of different velocities,
as the outside of a curve has always greater speed than the inside;
consequently the outer edge is eroding while the inner is depositing
sediment. The Colorado River, in the lower part of its course from Yuma
down, overflows its flood plain, and deposits thereon a certain amount
of sediment during every high water. This flood plain extends back for
several miles on the west bank, showing a succession of benches or
levees running parallel with the stream on a higher level than the back
country. The water, when high enough to reach over these benches,
gathers in the back part, where it evaporates, leaving a mud that
greatly enriches the soil. These levees are the result of the law quoted
above, as the water in the regular channel flows swifter than on the
flood plain; consequently on the border of the two a large amount of
sediment is thrown down. As these border lands are only covered during
the highest floods, they maintain a growth of willows and poplars that
gives the banks a greater stability, and preserves them to a certain
extent from the erosive force of the current.
A source of changes in the direction of the main current is the
stranding of logs and tree tops brought down from the upper courses of
the river, as the sediment accumulates behind them and forms islands in
midstream. Several of these are to be seen in the river channel in
passing down the stream.
From soundings made across a section of the river at the railroad bridge
at Yuma, the depth was found to vary from 2½ feet to 21 feet. At the
meter placed in the main channel the indicator showed a depth of 17
feet.
At ordinary high water, caused by the annual rising of the Gila River,
or of the Colorado in its upper reaches, which events usually occur at
different seasons of the year, the meter has not been known to show a
depth of over 28 feet, but in consequence of a co-equal rise in both
streams during the past season, the meter registered over 33 feet. This
excess filled the river swamp on the right bank, where the erosive force
of the current was most effective.
The course of the river below Yuma for several miles is to the west,
until the neighborhood of El Rio station is reached, where sandstone
bluffs on the right bank deflect the current back to its general south
course. A little back from the river below this point is a small,
isolated range of hills, known as Pilot Knob, formed of granite,
fissured with seams of dioritic rock. The granite shows lamination, and
the surface of the rocks is polished by the constant attrition of the
drifting sands. The beach near Pilot Knob is cemented into a calcareous
conglomerate, underlaid by sand in a loose state. After resuming its
southern course the river for several miles follows a straight reach,
until below Hanlon’s Ferry. The tendency of the current to bear more to
the right bank shows itself now in the formation of sloughs and inlets
that absorb a large proportion of the water and form several islands,
shallowing that part of the river that passes down the proper channel.
[Illustration: _SECTION OF COLORADO RIVER AT YUMA_]
[Illustration: _DETAIL OF BREAK
IN
COLORADO RIVER_]
The accompanying sketch shows the different channels in detail. Formerly
the water from these outside channels returned through the bend marked
“sand” to the main stream, but at the present time it passes through a
crevasse in the bend, marked Tapscott and Carter Rivers, furnishing the
largest portion of the water that ultimately found its way into the
depression of Salton Lake. During the extreme high water the western
bank from El Rio down, which is formed entirely of silt, was broken
through in numerous places, and the mostly shallow channels either
entered the river again below, or accumulated their waters on the back
part of the flood plain, and by following the natural hollows and
gullies gradually wound their way in the direction of the old Yuma road.
The great force of the current soon cut down below the level of the
river bed and relieved in part the congested condition. The grade being
gradually to the west, the water cut through the sediment in that
direction, partly to the Yuma road, partly farther south parallel to the
Rio El Medio, which, judging from analogy, owes its origin to some
former similar condition of the river.
Tapscott River may have been formed prior to Carter River, as it has a
better defined channel; the latter has no regular channel, but seems to
have been caused by the excess of water that could not enter the former,
following depressions and sloughs which have no direct connection with
one another. At the time these observations were made, the estimated
volume of water in the river at the Yuma bridge was about 3,700 cubic
feet per second, and at the crevasse forming Tapscott and Carter Rivers,
two fifths of the entire volume of water in the river was passing
through, but none of it was reaching Salton Lake. Of this two fifths not
more than 20 cubic feet per second was running through Carter River.
Beyond Alamo Mocho, which is on the old Yuma road, at the time of the
flood, the water flowed into a number of lagoons, and thence into New
River, following the old channel that was cut at the time of the 1849
overflow, and thus reaching and forming Salton Lake. All of the water
leaving the main river at present finds its way down through the Hardy
Colorado back to the Colorado proper, or evaporates.
In the beginning of this article mention was made of a borehole that was
sunk by the new Liverpool Salt Company in the salt marsh, and which
revealed under a thin crust of mud and salt a depression filled with
ooze, composed largely of magnesium and sodium salts. This ooze is
probably the final resultant of the evaporations of the former sea
water, and which, from the well-known avidity of the magnesian salts for
moisture, is kept in this condition of ooze through the natural drainage
and seepage waters. This depression may extend beyond the borders of the
present marsh toward the gulf, covered over by the sand, and may have
some relation with the small so-called mud volcanoes southeast of the
lake near the station of Volcano, as well as with some openings in the
ground mentioned by one of the gentlemen who investigated these regions
between the Colorado River and the lake, and of which he stated that any
amount of water running into them did not seem to fill them. Should such
a connection exist, the water pouring in from the river would have
dissolved the thin salt crust where exposed, and opened a channel,
permitting a rapid filling in of the water which formed the lake, for
otherwise a body of water running over this light sand and under such a
dry, hot temperature would hardly have filled up the depression as
rapidly as was the case. Besides, this would explain the reason for the
fresh waters of the Colorado River attaining so rapidly a density of
over 20° Baumé. Should this supposition prove correct, and it could
easily be ascertained by a series of shallow boreholes, it might be
expected that every large overflow in the Colorado River in this
direction would result in a repetition of Salton Lake.
Transcriber’s Notes
—Retained publication information from the printed edition: this eBook
is public-domain in the country of publication.
—Silently corrected a few palpable typos.
—Transcribed handwritten in-photo captions.
—In the text versions only, text in italics is delimited by
_underscores_.
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