ore
treated in gold and silver mills of the United States increased from
8,528,596 short tons in 1910 to 9,325,090 short tons in 1911. Increases
in tonnage milled arc noted particularly for Alaska, California,
Nevada, New Mexico, and South Dakota, and considerable decreases for
Colorado. The total quantity of gold recovered by mills in 1911 was
2,440,339 fine ounces, against 2,366,322 ounces in 1910, with increased
output from Arizona, Nevada, New Mexico, and South Dakota (notably),
and decreases in most of the other States. The total silver recovery in
mills was 9,662,545 fine ounces in 1911, against 8,245,851 ounces in
1910. There was considerably increased production of silver from mills
in Colorado, Montana, Nevada (notably), New Mexico, South Dakota,
Texas, and Utah in 1911.
Under
the third item is given the quantity of ore treated for concentration
only, including the large quantities of copper, lead, zinc, and mixed
ores, whose concentrates are smelted primarily for these metals, the
gold and silver being recovered in refining the copper, lead, and zinc.
Examples are the copper ores of the disseminated deposits of Bingham,
Utah, the ores of Butte, Mont., the lead ores of the Coeur d'Alene,
Idaho, and some of the lead-zinc and mixed ores of Leadville, Colo. The
quantity of concentrates produced and the recoverable gold and silver
content, however, as- already stated, represent not only the
concentrates from these straight concentrating mills but also those
from gold and silver mills. The concentrates are mainly smelted, as
stated, but are in some cases treated in gold and silver mills by the
processes named. Comparison with corresponding figures published by the
Survey for 1910 show that the total tonnage treated in straight
concentrating mills increased from 15,407,517 short tons in 1910 to
17,602,315 tons in 1911, the greater part of the increase being
credited to Arizona, Idaho, Nevada, and Utah. The total gold and silver
bearing concentrates produced in all classes of mills increased in
quantity from 2,597,992 short tons in 1910 to 2,773,870 tons in 1911,
the increases being mainly in Arizona, Idaho, Montana, Nevada, and
Utah. The total recoverable gold content of the concentrates increased
from 475,452 fine ounces in 1910 to 484,971 ounces in 1911, the
increases being chiefly in Alaska, Arizona, California, Nevada, New
Mexico, and Utah, and the decreases mainly in Colorado and Montana. The
silver in concentrates produced increased from 19,949,379 fine ounces
in 1910 to 20,794,441 ounces in 1911, the increases being most notable
in Arizona, Idaho, New Mexico, Oregon, and Utah, and the decreases in
Colorado and Montana.
The
fourth item covers quantity and recoverable precious-metal content of
crude ore shipped direct to smelters from the mines, and in general
includes the richer gold, silver, copper, lead, and zinc ores from
which the gold and silver are eventually recovered by refining the
copper or lead bullion that collects the precious metals in the
smelting. The total quantity shipped of this class of ore decreased
from 6,016,425 short tons in 1910 to 5,588,771 tons in 1911, the
decreases being mainly in Arizona and California, and increases being
recorded for most of the other States. The tonnages are notably large
for Arizona and Utah, and the bulk of the precious-metal producing
ores of the Eastern States are smelted crude. The total gold output
from crude smelting ores decreased from 623,272 fine ounces in 1910 to
611,344 ounces in 1911, the decreases being chiefly in California,
Colorado, Nevada, and South Dakota, and increases being
