The
mine production of silver from the three most important sources of
silver—dry and siliceous ores, copper ores, and lead ores—was 94.54 per
cent of the total output in 1921, against 87.90 per cent in 1920. The
percentage of the total output from dry and siliceous ores increased
15.66 per centin 1921, and that from lead ores 2.11 percent; that from
lead-zinc ores decreased 4.26 per cent, and that from copper ores 11.13
per cent. The combined yield of silver from placer bullion, zinc ores,
and copper-lead was only 1.16 per cent of the total.
PLACERS.
The
output of silver from the refining of placer gold was 8,000 ounces more
than in 1920. Of the total production 75 per cent came from Alaska and
California.
DRY AND SILICEOUS ORES.
About
27 per cent of the mine production of silver from dry and and siliceous
ores was from Nevada (chiefly from the Tonopah district), more than 25
per cent from Utah (mainly from the Tin tic district) , and nearly 20
per cent from Colorado. There were increases in the quantity of silver
from siliceous ores in a few of the States especially in California,
Colorado, and Utah.
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 then recovered by refining the mill bullion. The remainder is
produced 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
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 cnalcopyrite 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, though the
output was only 1,663,472 ounces in 1921, against 6,030,507 ounces in
1920. Arizona was next, with 1,241,436 ounces in 1921, against
3,716,246 ounces in 1920; Alaska ranked third, with 545,229 ounces in
1921, against 682,033 ounces in 1920; and Utah produced 229,556 ounces
in 1921, against 452,915 ounces in 1920. 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 County. 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.
