Leadville,
Upper San Miguel, and Sneffels districts). The quantity of silver from
siliceous ores mined in Utah decreased from 3,987,068 ounces in 1918 to
3,645,909 ounces in 1919. There were decreases in many of the States,
especially in Nevada, where the production in 1919 was 2,845,793 ounces
less than in 1918 and 6,445,328 ounces less than in 1916. Arizona and
Montana also each produced more than 1,000,000 ounces of silver from
this source, California 547,541 ounces, and New Mexico nearly 541,000
ounces, and the production of silver in these States from siliceous
ores increased considerably. More than 99 per cent of the 538,642
ounces of silver produced in Texas was from siliceous silver ores.
A
large part of the silver from gold-silver siliceous ores is obtained
with the gold by amalgamation and cyanidation in the mills, and the
silver is recovered by refining the mill bullion. The remainder is
p
roduced by smelting
the richer ores and refining the copper or lead bullion produced. A
small quantity of silver was also recovered from the leaching of copper
ores.
COPPER ORES.
The
mine production of silver from domestic copper ores in 1919 was
12,880,624 fine ounces, against 20,462,597 fine ounces in 1918. The
decrease in production of silver from copper ores mined in Alaska was
231,357 ounces; Utah, 859,142 ounces; Nevada, 205,244 ounces; Michigan,
68,037 ounces; California, 320,231 ounces; Montana, 4,179,394 ounces;
and Arizona, 1,636,566 ounces.
The
silver produced from copper ores is obtained in the electrolytic
refining of Lake and blister copper produced by smelting. The copper
ores are mainly sulphides (except the Lake ores of Michigan, which are
native metal in amygdaloid and conglomerate matrix), and a greater
quantity contains chalcocite than chalcopyrite or cupriferous pyrite.
The silver tenor of the extensive disseminated deposits of the Santa
Rita district, N. Mex., and of Ely, Nev., is notably low, but similar
deposits elsewhere add considerable quantities of silver.
In
output of silver from copper ores Montana continued to lead with
6,341,825 ounces in 1919, against 10,521,219 ounces in 1918. Arizona
was next with 3,711,052 ounces in 1919, against 5,347,618 ounces in
1918; Utah ranked third with 586,417 ounces in 1919, against 1,445,559
ounces in 1918; and California produced only 349,480 ounces in 1919,
against 669,711 ounces in 1918. The production of Montana comes mainly from Butte, that of Arizona chiefly from
Bisbee and Jerome, that of Utah from Tintic and Bingham, and that of
California from Plumas, Shasta, and Calaveras counties. Of these
districts Bisbee well represents the disseminated type; Bingham
produces from both lode and disseminated deposits; and the remainder
produce silver chiefly from copper ore mined from deep lodes.
LEAD ORES.
The
mine production of silver from argentiferous lead ores in 1919 was
14,351,293 fine ounces, against 18,291,243 fine ounces in 1918 and
19,096,474 ounces in 1917. The output from Idaho decreased
