Figures
corresponding to those in this table were collected and compiled for
the entire United States by the Survey for the first time in 1911, and
comparison for four years can therefore now be made.
The
total quantity of crude ore treated and old tailings re-treated in gold
and silver mills in 1914 was 9,849,085 short tons in 1914, against
9,401,856 tons in 1913, against 9,677,360 tons in 1912, and 9,670,483
tons in 1911.
The
great bulk of the ore treated, as shown, was milled in South Dakota,
California, Alaska, Colorado, and Nevada, in the order named, and here
the famous mills of the Homestake, Mother Lode and Grass Valley,
Treadwell, Cripple Creek, Tonopah, and Goldfield mines arc especially
in evidence. Large numbers of smaller mills, however, mark the wide
distribution, of gold mining especially, in nearly every mountain
range. These plants range from small prospecting mills with from 1 to
3 light stamps, simple amalgamating apparatus, and usually no
concentrating apparatus, through the conventional 5-stamp, 10-stamp,
15-stamp, and 20-stamp mills— with plants varying widely, according to
characteristics of local ore, in weight and drop of stamps, rapidity
and fineness of discharge, and arrangement for amalgamation,
concentration, and cyanidation—to the great mills above mentioned,
which treat enormous quantities of
