and
Idaho. The total recoverable content of all concentrates was 438,450
ounces in 1918, against 488,297 ounces in 1917, and 547,172 ounces in
1916, and came mainly from California, Colorado, Utah, Alaska, and
Nevada, in the order named. The total recoverable silver from
concentrates produced was 27,106,268 ounces in 1918, against 26,219,931
fine ounces in 1917 and 29,566,150 ounces in 1916, and nearly one-half
the total came from Montana—Idaho, Colorado, Utah, Arizona, and Nevada
being the other States in which large quantities of silver were
recovered from concentrates. The increase was entirely owing to a
larger output in the silver in concentrates derived from ores mined in
Montana.
The
fourth item covers the quantity and the recoverable precious-metal
content of crude ores shipped from the mines direct to the smelters,
and in general includes the richer gold, silver, copper, lead, and
mixed ores from which the gold and silver is eventually recovered by
refining the copper or lead bullion that collects the precious metals
in the smelting. The total quantity shipped of this class of ore
decreased from 8,894,609 short tons in 1916 and 8,645,869 tons in 1917
to 7,816,091 tons in 1918. The output was notably from Arizona, which
produced nearly one-half of the ore directly smelted, followed by Utah,
Nevada, Eastern or Appalachian States, Montana, California, and
Colorado, in the order named. The total yield of gold from crude ores
smelted decreased from 434,743 fine ounces in
1917 to
336,934 ounces in 1918, and came chiefly from Arizona, Utah, Colorado,
Montana, Nevada, and California, in the order given. The total
recoverable silver output decreased from 30,758,752 fine ounces in 1917
to 29,298,637 ounces in 1918, and was notably from Utah, Arizona,
Colorado, Idaho, Montana, Nevada, California, and New Mexico. Utah and
Arizona produced more than half of the silver recovered from crude ore
smelted.
Under
the fifth item is given the quantity of old materials, principally
tailings and slags, re-treated, and also the ore and tailings leached,
and their recoverable contents. These are partly smelted, often for
their fluxing as well as their metal value; but considerable quantities
of old tailings are now concentrated and cyanided, and the impounding
of mill tailings for future treatment as well as because of legal
requirements has now become a general practice. The total quantity of
all old material treated as shown in the table increased from 2,055,009
short tons in 1917 to 4,167,837 tons in 1918. The increase in quantity
of old material treated in 1917 and 1918 (only 894,030 short tons were
treated in 1916) was due mainly to the high prices of copper and lead.
Most of the gold and silver derived from old tailings is included under
recoveries by amalgamation and cyanida-tion at gold and silver mills.
The total quantity of ore leached in
1918 was
2,127,599 short tons, of which 1,776,000 were from Arizona mines,
282,894 tons were from Utah mines, 68,502 tons from Montana mines, and
203 tons from Nevada mines. The total quantity of old tailings and slag
concentrated or directly smelted in 1918 was 2,040,238 tons, most of
which was from Montana, Utah, and Nevada.
