The
first column in the table takes no account of placer gravel but
represents the output of mines producing ore only. The greatest output
was made in Arizona, Utah, and Montana, all notable for large yields of
copper ores; in Idaho, a large producer of lead ores; in Alaska,
California, and Nevada, large producers of both copper and siliceous
ores; in South Dakota and Colorado, large producers of siliceous ores;
and in New Mexico, a large producer of copper ores.
Many
gold and silver mills employ concentrating apparatus, and the
concentrates they obtain are combined in the table with those from
straight concentrating mills under the heading "Concentrates produced.'
The gold and silver included in this item are recovered partly by
amalgamation and cyanidation, as is shown in detail in the table on
page 631 of this report.
The
figures for the quantity of ore treated by concentration include only
the large quantities of copper, lead, zinc, and mixed ores whose
concentrates are smelted primarily for these metals, the gold and
silver being recovered in refining the copper and lead bullion and
smelting the zinc residues. Examples are the copper ores of the
disseminated deposits of Bingham, Utah, and of New Mexico and Nevada;
the copper ores of Butte, Mont., and Ely, Nev.; and the lead and
lead-zinc ores of Coeur d'Alene, Iaaho, Butte, Mont., and Lead-ville,
Colo. The quantity of concentrates produced and the recoverable gold
and silver content represent not only the concentrates from these
straight concentrating mills but also those from gold and silver mills,
which form, however, a very small part of the total quantity of
concentrates and are derived mainly from Alaska, California, and
Colorado ores. These concentrates are mainly smelted but are also
treated in gold and silver mills by the processes named.
The
ore treated in straight concentration mills increased more than 100 per
cent in 1922, mainly because of the resumption of operations at copper
mines in Arizona, Montana, Nevada, Utah, and other States. Montana
mills produced the largest quantity of concentrates, followed by those
of Arizona, Utah, and Idaho. The recoverable gold content of
concentrates came mainly from California, Utah, Colorado, Montana,
Alaska, Arizona, Oregon, and Nevada. About 63 per cent of the
recoverable silver from concentrates produced came from Montana and
Idaho, and large quantities came from Colorado and Utah. The increase
was due mainly to larger quantities of silver in concentrates derived
from ores mined in Montana, Utah, California, Colorado, Nevada, and
Arizona.
The
figures for the quantity and the recoverable precious-metal content of
crude ores snipped from the mines direct to the smelters in general
include 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. Arizona produced about 46 per cent of the ore directly
smelted and was followed by Utah, Tennessee, Colorado, Montana, Nevada,
New Mexico, and Idaho. Utah and Arizona produced 62 per cent of the
silver recovered from crude ore smelted.
The
old materials, principally tailings and slags, re-treated (with which
are included ore and tailings leached) 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
