Figures
corresponding to those in this table have been published for the entire
United States by the Geological Survey since 1911. The quantity of
crude ore treated and old and new tailings re-treated in gold and
silver mills reached a maximum in 1915 (11,878,287 tons). Itexceeded
11,000,000 tons in 1916 and l917, but has declined steadily since the
record year, except for a small increase in 1919.
The
great bulk of the ore treated was milled in Alaska, South Dakota,
Colorado, California, Nevada, and Arizona, and here the famous mines
and mills of the Homestake, Mother Lode, Grass Valley, Treadwell,
Cripple Creek, Tonopah, Goldfield, and San Francisco (Oatman) districts
are especially noteworthy. Large numbers of smaller mills, however,
mark the wide distribution of gold mining in these regions and in many
other scattered districts.
The
total yield of gold by amalgamation in the United States in 1921 was
765,397 fine ounces, against 679,409 fine ounces in 1920, and there has
been a decrease of about 199,200 ounces since 1916. Appreciable
decreases were shown in Alaska, Nevada, New Mexico, and Montana, and
there were increases in South Dakota, California, Colorado, Washington,
Oregon, and Idaho.
The
silver produced by amalgamation came mainly from California, South
Dakota, Alaska, Colorado, and Nevada, and consisted chiefly of silver
alloyed with gold.
