placer
concentrates from these localities received at the Survey do not
contain platinum; yet they are so few in number and so small in size
that they can not be said to prove or disprove the absence of platinum
in those placer gravels. Day's i work showed the
presence of platinum in concentrates from near Columbia and Prescott,
in Yavapai County. It is also reported that the gravels of Colorado
River carry platinum as well as gold. These placers have been worked in
places. The largest accumulations of gravels appear to be below the
mouth of the Grand Canyon and to extend from Grand Wash for several
miles below the mouth of Virgin River.
CALIFORNIA.
Placer
mines in Butte, Humboldt, Plumas, Sacramento, Stanislaus, Trinity, and
Yuba counties produced over 600 ounces of crude platinum in 1915. The
greater part of this output was made by dredges, but some platinum was
recovered by hydraulic mines and a small quantity from beach deposits.
As stated elsewhere in this report, it is believed that, with adequate
provision, the placer deposits of California are capable of producing
much more platinum than they do.
NEVADA.
The
Boss mine, near Good Springs, Clark County, Nev., was developed for the
first 11 months of 1915 by the Platinum Gold Mining Co. under option.
Owing to a provision of the contract, no platinum ores were marketed
during the operations of this company. On December 1 the property
reverted to the original owners, the Boss Mine Co., which reported that
a considerable quantity of platinum ore is blocked out and that active
development will continue. It is said that platinum ore has been
developed to a vertical depth of 150 or 200 feet on the dip of the
ledge. Experiments are now under way to develop a method of treatment
to separate the platinum-bearing minerals from gangue and copper ores.
OREGON.
Only
one mine in Oregon reported a production of platinum in 1915. This is
on a beach deposit located in Curry County. Platinum is known to occur
in other beach deposits on the southern coast and also in the vicinity
of Kerby in Josephine County.
WASHINGTON.
Samples
of placer concentrates said to have been obtained from the south fork
of Lewis River in Clark County, Wash., have been received by the
Survey, in which there is an appreciable quantity of plantinum and
gold. This is of particular interest, as it indicates that the older
metamorphic series must rise abruptly to outcrop on Lewis River. These
earlier rocks are entirely covered by the Columbia River lava only a
few miles south of this region.
'
Day, D. T., and Richards, R. H., Blacksands of the Pacific slope: U. S.
Geol. Survey Mineral Resources, 1905, pp. 1180-1181, 1906.
