ounces.
The 3 most prominent localities are the Camp Floyd (Mercur) district in
Utah, the Black Hills of South Dakota, and the Moccasin Mountains of
Fergus County, Mont.
The
dry or siliceous ores further include the quartzose ores of Cripple
Creek, Colorado, in which the prominent characteristic is the
occurrence of large quantities of gold tellurides. These ores are
partly smelted, partly chlorinated, and partly cyanided, all three
processes being applicable.
There
is, finally, a large class of dry ores which contain pyrite and other
sulphides, and which are best treated by the smelting process, with or
without concentration. Colorado contributes by far the largest quantity
of these ores, among which those of Leadville are of particular
importance.
Copper ores.—In
1906, 271,197 ounces of gold were obtained from copper ores, against
255,568 ounces in 1905. This moderate gain contrasts with the great
increase in tonnage of copper ores treated, but is of course due to
their ordinarily low tenor in gold and silver. The important States
rank as follows: Utah, Arizona, Montana, California. The richest ores
are obtained from the Bingham and Tintic districts in Utah, giving a
total for the State of 120,767 ounces, a slight decrease from the
figures of 1905. Arizona copper ores are generally poor in gold and
silver, but the richer ores from the United Verde raised the gold from
this source to 62,299 ounces, a jconsiderable increase over 1905. The
copper ores of Butte yielded a little more than in 1905 in spite of a
decreased copper production, the total for Montana being 55,054 ounces.
Renewed activity in Shasta County added to California's share of gold
from copper ores, and recently developed copper mines in the Coeur
d'Alene district increased Idaho's output.
With
few exceptions the copper ores are of the sulphide class, containing
either chalcocite or chalcopyrite. A large majority of them are
concentrated and smelted, the gold being recovered during the
electrolytic refining of the copper.
Lead ores.—From
lead ores proper only 60,812 ounces of gold were recovered. This was
less by about 6,000 ounces than in 1905, and emphasizes the scantiness
of the supply of higher grade lead ores. Heavy losses were recorded in
Colorado, Montana, and Utah, but were partly offset by smaller gains in
Arizona and Nevada. In gold from lead ores the States rank as follows:
Colorado, Arizona, Utah, Montana, Nevada, Idaho. The gold from Idaho
lead ores has been partly overlooked in earlier statistics. It is
present, however, to the amount of from 25 to 50 cents per ton in the
heavy shipments of Coeur d'Alene concentrates, and most of it is
undoubtedly recovered. The larger part of the lead ores are
concentrated before smelting. The oxidized ores form only a very small
percentage of the total.
Zinc ores and mixed ores.—Only
a very small amount of gold is recovered from zinc ores. Together with
the silver it remains in the cinders after the distillation of the
zinc, and these cinders, if of sufficiently high grade, are sold to
the lead smelters. The lead-zinc ores are generally concentrated to
effect the separation of the galena and sphalerite. A total of 11,691
ounces of gold was recovered from these ores, which were derived almost
wholly from Colorado. The copper-lead sulphide ores are almost wholly
confined to Utah and
