lead
bullion and smelting the zinc residues. Examples are the copper ores
of the disseminated deposits of Bingham, Utah, the copper ores of
Butte, Mont., the lead and lead-zinc ores of Coeur d'AIene,
Idaho, Butte, Mont., and Leadville, Colo. The quantity of concentrates
produced and the recoverable gold and silver content, however, as
already stated, represent not only the concentrates from these straight
concentrating mills but also those from gold and silver mills. These
concentrates are mainly smelted but are in some cases treated in gold
and silver mills by the processes named. The tonnage treated in
straight concentration mills decreased from 27,088,716 short tons in
1913 to 24,306,504 tons in 1914, mainly because of the curtailment of
activity at copper mines. Utah ranked first in quantity of ore
concentrated, followed by Arizona, Montana, Nevada, Idaho, and New
Mexico. These tonnages, with the exception of those of Montana and
Idaho, represent largely tonnages of low-grade disseminated copper ores
milled. The total quantity of gold and silver-bearing concentrates from
all classes of milling ore decreased from 3,786,031 short tons in 1913
to 3,613,024 tons in 1914. Montana mills produced the largest quantity
of concentrates followed by those of Utah, Nevada, Arizona, and Idaho.
The total recoverable gold content of all concentrates was 466,620
ounces in 1914, against 473,788 in
1913, and
came mainly from Colorado, California, Alaska, Utah, and Montana, in
the order named. The total recoverable silver from concentrates
produced was 24,102,264 fine ounces in 1914, against 24,045,495 ounces
in 1913, and came chiefly from Idaho, Montana, Utah, Colorado, and
Nevada.
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 ore 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 7,109,088 short tons in 1913 to 6,292,218 tons in
1914.
The output was notably from Arizona, followed by Utah, Montana,
Colorado, Eastern or Appalachian States, California, and Nevada in the
order named. The total yield of gold from crude ores smelted increased
from 568,064 fine ounces in 1913 to 604,113 ounces in 1914, and came
chiefly from Colorado, Utah, Montana, Arizona, and Nevada in the order
given. The total recoverable silver output decreased from 31,436,284
fine ounces in 1913 to 28,841,241 ounces in 1914 and was notably from
Utah, Colorado, Idaho, Montana, and Arizona.
Under
the fifth item is given the quantity of old materials, principally
tailings and slags, re-treated, and their recoverable contents. Th^se
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 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 decreased from 524,517 short tons in 1913 to 319.204
tons in 1914, and the recoverable content of gold decreased from 14,119
to 4,880 ounces, and that of silver decreased from 491,270 to 394,005
ounces. The silver yield was largely from Utah.
