GOLD AND SILVER.
879
The
first item consists of all classes of ores, tailings, and slag
producing gold and silver in the United States in 1913. The grand
total shows that this tonnage increased from 30,287,175 short tons in
1910 to 32,928,522 tons in 1911, to 38,594,806 tons in 1912, and to
43,984,220 tons in 1913. This takes no account of placer gravel but
represents output of mines producing ore only. The most important
increases in material sold or treated were from 6,840,082 tons in 1912
to 7,931,862 tons in 1913 in Arizona, from 2,576,626 to 2,734,866 tons
in Colorado, from 2,266,334 to 2,451,592 tons in Idaho, from 5,552,164
to 5,960,118 tons in Montana, from 4,763,965 to 5,367,211 tons in
Nevada, from 1,352,286 to 2,217,660 tons in New Mexico, and from
7,770,270 to 10,202,566 tons in Utah. Decreases were noted for Alaska,
California, and South Dakota in 1913.
In
reference to the second item, many gold and silver mills employ
concentrating apparatus, and the concentrates resulting are combined
in the table with those from straight concentrating mills, under the
heading ''Concentrates produced." The gold and silver recovery under
this item is mainly by amalgamation and cyanidation, as is shown in
detail in the last table of this report. The total quantity of crude
ore treated in gold and silver mills of the United States increased
from 8,528,596 short tons in 1910 to 9,325,090 tons in 1911 and to
9,367,335 tons in 1912, but decreased to 9,261,899 tons in 1913.
Increases in tonnage milled are noted for Arizona, from 198,262 tons in
1912 to 199,980 tons in 1913, for Colorado from 1,435,837 to 1,610,335
tons, for Nevada from 1,309,339 to 1,451,485 tons, for New Mexico from
106,208 to 124,536 tons, and for South Dakota from 1,893,836 to
1,895,445 tons. The principal decreases were from 1,761,799 to
1,614,506 tons in Alaska, from 2,077,300 to 1,905,258 tons in
California, from 205,409 to 173,440 tons in Montana, and from 171,117
to 75,972 tons in Utah. The total quantity of gold recovered by mills
in 1913 was 2,179,348 fine ounces (valued at $43,581,354), against
2,262,951 ounces in 1912, 2,440,339 ounces in 1911, and 2,366,322
ounces in 1910. There was increased output of gold from nulls in
Arizona, Colorado, and New Mexico, and decreased production from
Alaska, California, Montana, Nevada, South Dakota, and Utah. The total
silver recovery in mills was 14,492,424 fine ounces in 1913, against
12,475,279 ounces in 1912, 9,662,545 ounces in 1911, and 8,245,851
ounces in 1910—a continued and marked trend upward. There was increased
silver production from mills in Arizona, Colorado, Montana, Nevada
(notably in 1913, as in 1912 and 1911 also), New Mexico (notably), and
Texas, and decreased output from California, Idaho, South Dakota, and
Utah.
Under
the third item is given the quantity of ore treated by 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 and lead bullion
and smelting the zinc residues. Examples are the copper ores of the
disseminated deposits of Bingham, Utah, the copper ores of Butte,
Mont., the lead and lead-zinc ores of the Coeur d'Alene, Idaho, Butte,
Mont., and Leadville, Colo. The quantity of concentrates produced and
the recoverable gold and silver content, however, as already stated,
represent not onlv the concentrates from these straight concentrating
mills but also those from gold and silver mills.
