in
valuable quantity, and it was in the course of this sampling that the
platinum and palladium content of the ore was discovered.
The
deposit at the Boss mine consists of a fine-grained quartz mass, which
in the main replaces iregularly the Carboniferous dolomites along a
series of vertical fractures. A small mass or dike of granite porphyry
intrudes the dolomite about 600 feet north of the mine, but no basic
intrusives occur; in fact, none are known to occur in the Yellow Pine
mining district, which is the most productive lead-zinc district in
Nevada. The ore bodies so far developed may be briefly described as
oxidized copper shoots and gold-platinum-palladium shoots. The copper
ores consist largely of chrysocolla and other oxidized compounds, but
these ores carry only minor quantities of the precious metals. The
gold-platinum-palladium shoots consist of a fine-grained quartzose ore
containing a small quantity of a bismuth-bearing variety of the rare
mineral plumbojarosite (a hydrous sulphate of iron and lead). The
principal ore shoot disclosed by the present workings forms an
irregular pipe, pitching at a low angle to the northeast. In this
shoot, at the time of visit, from 1,000 to 2,000 tons of ore had been
developed, which averages, in ounces to the ton, gold, 3.46; silver,
6.4; platinum. 0.70; and palladium, 3.38. The precious metals are
associated especially with the plumbojarosite; pockets of the pure
mineral carry 100 ounces or more of platinum and palladium and several
hundred ounces of gold to the ton. This great richness points to a
concentration of the precious metals in the oxidized ore by surface
solutions, so that in depth the pockets of extremely high-grade ores,
such as are now being extracted, will give place to ore of moderate
grade. The only sulphide so far found in the mine is chalcocite, and
this is probably of secondary origin.
The
gold-platinum-palladium deposit at the Boss mine differs greatly from
any described deposit carrying platinum metals. Further, its probable
genetic connection with siliceous igneous rocks is very remarkable, for
most primary platiniferous deposits are genetically associated with
basic igneous rocks. The Boss lode is one of the few primary deposits
in which platinum metals occur in more than traces, and with one
possible exception (the new Rambler mine in Wyoming) is the only
primary deposit of economic importance in which these metals are the
constituents of predominant value.
OREGON.
The
larger part of the platinum obtained in Oregon in 1914 came, as usual,
from beach workings in the vicinity of Bandon, Bullards, and
Marshfield, though some was obtained in hydraulic workings near Galice,
Kerby, and Waldo. No new discoveries of platinum of importance were
made in this State in 1914. The Sweet machine is in use at several
properties and from all reports appears to be making satisfactory
recoveries. It seems probable that 1915 will witness decidedly larger
operations in Oregon.
WYOMING.
At
the Rambler mine in Albany County, Wyo., little new ore was raised in
1914, but the 50-ton mill was rebuilt and a Peck centrifugal
concentrator was installed* during the latter part of the year. It is
understood that some ore from the bins was put through this machine and
that a satisfactory saving of platinum and palladium was accomplished.
FOREIGN.
COLOMBIA.
As
stated in the report for 1913, the principal platinum producing region
in Colombia is on Atrato and San Juan Rivers and their tributaries in
the Choco district. Late in 19142 an English company se-
iMin. and Eng. World, vol. 41, p. 1155, 1914.
2 Eng. and Min. Jour., vol. 98, p. 861, Nov. 7, 1914.
