Figures
corresponding to those in this table have never before been compiled
for States or for the country as a whole, and the Survey made special
efforts to secure the information given for 1911. Comparisons can not
be made, therefore, with data for preceding years.
As
shown in this table, the total quantity of crude ore and old tailings
treated in gold and silver mills in the United States in 1911 was
9,670,483 short tons.
The
great bulk of the ore treated, as shown, was milled in California,
South Dakota, Alaska, Colorado, and Nevada, and here the famous mills
of the Mother Lode and Grass Valley, the Homestake, the Treadwell, and
those of Cripple Creek and Goldneld and Tonopah are especially in
evidence. Large numbers of other mills, however, mark the gold and
silver mining industries in every mountain range and region where
essentially gold and silver ores are mined. These plants range from
small prospectors' mills with from 1 to 3 light stamps, simple
amalgamating apparatus, and usually no concentrating tables, through
the conventional 5-stamp, 10-stamp, 15-stamp, and 20-stamp mills—with
plants varying widely according to local ore characteristics in weight
and drop of stamps, rapidity and fineness of discharge, and arrangement
for amalgamation and concentration— to the great mills above mentioned,
which treat enormous tonnages daily and represent the high-water mark
in milling and metallurgy of the precious metals, equipped as they are
with intricate and beautifully balanced apparatus for sorting,
crushing, sizing, classifying, grinding, concentrating, and
amalgamation and cyanidation, and working with high extraction
efficiency and admirable organization of labor and machines. The
difficulties overcome in treating low-grade, refractory, and otherwise
difficult ores, and the results achieved in recent years are a monument
to American milling and metallurgy and an inspiration to the solution
of the relatively few remaining problems of the art. From time to time
new "processes" are
