famous
mills of the Mother Lode and Grass Valley, the Homestake, the
Treadwell, and those of Cripple dreek and Goldfield 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 announced and advocated for the extraction of gold
from low-grade or difficult ores, and although some of these are of
great merit and mark signal advances in the art as demonstrated in
actual practice in mining camps where their usefulness and
applicability are undoubt-edly proved, some of them are mainly
advertised in regions where money is always to be had for "get rich
quick" schemes and where personal knowledge of mining and metallurgy
are so rare that frauds readily flourish.
The
tonnages treated in gold and silver mills, with increases and decreases
for 1912, have been noted in connection with a preceding table.
The
total production of gold produced by amalgamation in the United States
in 1912 was 1,003,470 fine ounces, valued at $20,743,266, against
1,120,344 fine ounces in 1911. The decreases were mainly in Colorado,
Idaho, Montana, Nevada (notably), New Mexico, Oregon, and the southern
Appalachian States; the increases were chiefly in Alaska, California,
and South Dakota. California, South Dakota, Alaska, and Nevada were the
greatest producers of gold by amalgamation in 1912 in the order named.
The total production of silver by amalgamation was 795,755 fine ounces
in 1912, against 941,155 ounces in 1911. The output was largest in
Texas (where pan amalgamation has been chiefly practiced) and
California, ranking first and second, respectively.
The
total output of gold by cyanidation in 1912 was 1,386,526 fine ounces,
valued at $28,662,036, against 1,259,400 ounces in 1911. The bulk of"
the output was from Colorado, Nevada, South Dakota, Alaska, Arizona,
California, and Montana, in the order named, in 1912. The increases
were chiefly in Alaska, California, Colorado, and South Dakota (very
small), and the principal decrease was in Nevada, from 504,263 ounces
in 1911 to 444,633 ounces in 1912. The total output of silver by
cyanidation was 11,728,730 ounces in 1912, against 8,781,552 ounces in
1911, the principal increases being in
