OCCURRENCE OF PLATINUM IN LODE DEPOSITS.
DEPOSITS PREVIOUSLY KNOWN.
Although
the world's supply of platinum comes mainly from placer gravels, this
metal is known to occur in lode deposits, chiefly associated writh
iron and copper sulphides and probably of mag-matic origin. In the
nickel deposits of Sudbury, Ontario, platinum arsenide (sperrylite,
PtAs,) is found as small white cubes, with chalcopyrite and pyrrhotite.
Sperrylite is also known from the Rambler mine in Wyoming, where it is
associated with the copper ores, chalcopyrite and covellite, probably
of igneous origin and forming a lens in a dioritic rock. There has been
some commercial output of platinum concentrates from this mine.
Palladium is also present. Platinum, perhaps also as sperrylite, is
found in dikes of peridotite at Bunkerville, Nev., cutting pre-Cambrian
gneiss, associated again with chalcopyrite and pyrrhotite. Platinum
has been reported with wollastonite and grossularite garnet in a
contact metamorphic rock in Sumatra, and in quartz veins from southern
New Zealand, northern Finland, and Canada. Palladium has been found
with gold in a limestone in Brazil near the contact with an igneous
rock, and this alloy has also been reported in both placer and lode
deposits in the Kongo Free State. The gravel platinum of the Pacific
coast is probably derived from serpentine masses of the Sierra Nevada.
PLATINUM LODE DEPOSIT AT GOODSPRINGS, NEV.
In
August, 1914, while this chapter was in proof, a new discovery of
platinum in lode deposits was reported to the United States Geological
Survey, and efforts were made by the Survey to obtain some reliable
preliminary data for inclusion herewith in view of the threatened
shortage of Russian supplies due to the European war. For the
information following, thanks are due to Mr. Fred. A. Hale, jr.,
secretary of the Boss Gold Mining Co., of Goodsprings, Xev., upon whose
property the discovery was made. A geologic investigation of the
occurrence during the present field season is in prospect by the Survey.
The
property upon which the discovery was made is located about 10 miles
west of Goodsprings, and development work has disclosed a considerable
body of siliceous ore, carrying copper, gold, silver, and platinum,
occurring along a fractured zone in limestone and adjacent to a large
intrusion of quartz monzonite porphyry. Some very rich ore has been
reported, and at least 2,000 tons of ore carrying 1 ounce of gold to
the ton, with associated silver and platinum, were estimated to be in
sight in August. One carload of 23 per cent copper ore was shipped, and
a small shipment of gold ore averaging 124.8 ounces of gold per ton was
made. Later other small shipments of high-grade ore, and a 40-ton car
of ore assaying about 15 ounces of gold to the ton, were also reported.
Numerous assays indicated that the high-grade gold ore carried as high
as 65 ounces and the low-grade about 1 ounce of platinum per ton.
