an
average of twice as much silver as gold. As stated above, most of these
ores are now milled. Three-fifths of the product of Colorado was
derived from the ores of the "San Juan country," which are largely
gold-silver ores of milling grade with some smelting ores; there was no
decrease in the quantity from this source, but the great falling off
was in the low-grade ores from Leadville and Aspen, which contain
little gold but some lead, though not enough to be classed as lead
ores. The product of Montana is now mostly derived from Granite,
Jefferson, and Silverbow counties.
Silver
is recovered from siliceous ores by amalgamation or cyanide processes;
some rich siliceous ores are smelted, and the silver is obtained by
desilverization of lead bullion or by electrolytic refining of copper.
Copper ores.—From
copper ores 14,945,189 ounces were recovered in 1908, an increase of
almost 1,000,000 ounces as compared with 1907. The States ranked as
follows: Montana, Utah, Arizona, California, Idaho, Michigan, and
Colorado; none of the other States produced over 60,000 ounces. Here,
as in the gold production, the decreased output of the high-grade ores
of Bingham and Tintic camps in Utah was severely felt, causing a
decrease for Utah of 800,000 ounces. This was more than offset by an
increase of about 1,100,000 ounces in Montana derived from the greater
copper production of Butte, by an increase from Shasta County copper
ores of California of about 700,000 ounces, and by an increase of
800,000 ounces from the Arizona copper camps. The product of Arizona
was derived mainly from the Bisbee, United Verde, and Silver Bell
districts in the order named.
Lead ores.—The
total of silver derived from lead ores in 1908 was 15,148,764 ounces,
against 17,808,636 ounces in 1907. The important States ranked as
follows: Idaho, Utah, Colorado, Nevada, Montana, and Arizona. None of
the other States reached a production of 100,000 ounces from these
ores. The heavy decrease of about 2,600,000 ounces was mainly due to
Utah, which only produced 5,656,680 ounces in 1908, and here again the
cause was decreased activity at Bingham and Tintic districts, as well
as at Park City. In Colorado little change is noted. Comparatively
small quantities of high-grade lead ores come from Leadville, and the
silver product from this source was mainly derived from Creede and the
"San Juan country." Oxidized argentiferous lead ores are still
furnished by Tintic, Utah, Aspen, Colorado, and other places in
Colorado, Arizona, Nevada, and New Mexico.
Zinc and zinc-lead ores.—The
zinc ores proper contributed only a small output of silver; such ores
were shipped from Montana, Utah, and Arizona. The total product was
only 37,605 ounces. The zinc-lead ores are produced chiefly in Colorado
and in 1908 yielded about 723,000 ounces, against 1,475,000 ounces in
1907. They are usually concentrated into zinc and lead products. The
decrease in the activity of zinc mining resulted in a greatly reduced
yield. As usual, Leadville, in Colorado, contributed the greatest
output, but smaller quantities were also mined in Utah.
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