The silver state. [volume] (Winnemucca, Nev.) 1909-1925, 1921-09-13
TUNGSTEN MINING
NOT UNDERSTOOD

tungsten minerals. particularly as re-
fers to that ore formerly mined In
Humboldt county. will prove inter-
esting to readers. II follows:
For a long time it was supposed
that tungsten minerals were found
only in veins and pegmatite bodies,
but in 1907 and 1908, according to the
United States Geological Survey, De-
partment OF the Interior, sheelite was
discovered as minor mineral in con-
tact-metamorphic deposits in such
widely separated places as Japan,
Finland. Alaska and Nevada. The
Nevada deposit was at Browns, now
Toy, in Humboldt county, but, like
the others, II was of too low grade to
be mined at that time In competition
with the higher-grade veins of the
United States and other countries.
In 1915. after the World War had be-
gun. mining and milling were started
on the deposit at Browns and on de-
posits that had been more recently
discovered near Bishop, Calf. and in
1916 the price had risen so high that
prospecting for tungsten was carried
on vigorously all over the West and
numerous other contact-metamor-
phic deposits were found in various
parts OF the Great Basin In Nevada,
California and northwestern Utah.
Mining operations were begun on
many of them, so that in 1918 they
contributed very considerable part
OF the tungsten supply of the world,
furnishing an equivalent of 1,427
short tons of ore carrying 60 per cent
of tungsten trioxide.
All Observation-Disclosures depos-
Its carry tungsten in the form of
scheelite Calcium tungstate), with
here and there some secondary tung-
stem minerals. mostly tungstite
tungsten oxide). Wolframite and the
other original tungsten minerals are
wholly unknown In this type OF de-
posit
The deposits have been formed
through the alteration of limestone
and In less quantity of other rocks.
by solutions accompanying granite
intrusions. The solutions we're very
hot and carried number OF elements
besides tungsten. including silicon,
iron. aluminium. phosphorus. sulphur.
titanium. huorine. and chlorine. These
they exchanged for lime and carbon
dioxide. which they carried away,
leaving behind a rock composed of
varying quantities OF brown, green,
reddish, or colorless garnet. with cpl
dote. clinozosite. diopside. scheelite.
and other minerals, making a new
rock (tactite), which looks very little
like the limestone that is replaced
The sceelite In most deposits 10 In
comparatively small quantity, so that
the ore ordinarily carries less than
l per cent of tungsten trioxide. AL
though some masses of ore are of
higher grade, much more is OF lower
grade. The deposits are very irregu-
lar In form. and many thousands of
dollars have been lost because the
operators have not understood the
geology of ore deposits of this type
Similar deposits have been exploited
in japan. Chosen and Tasmania, but
those OF the United States are the
most extensive now known. 1t seems
probable that other deposits of this
type will be found In California. Ne
vada, and other States, also In China
and other countries.
A general study OF the deposits In
theUnited States has been made by
Frank L. Hess and Esper s. Larsen.
Of the United States Geological Sur
vey. and In the course of this work
two heretofore unknown deposits
were discovered by Mr.. Larsen. The
known deposits are described in Bull
letin 725-D which has just been is
sued by the Geological Survey.