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.