by
dry washing. There is a dry gold washing company which recently started
operations 2 miles south of Randsburg, and which, it is reported, is
meeting with some success. Some desultory work is being done in dry
washing at a few places along Colorado River in Riverside and San
Bernardino counties. The scattered claims are only worked occasionally.
From the Bonanza and Deep Diggings mines, in Red Rock district, Kern
County, some gold production is reported. The miners can not figure on
any average yield per cubic yard, for the gold is only found in spots,
and these are growing scarcer every day. Here, as at other places, .the
gravel wash or pay dirt lies at varying depths of 2 to 20 feet on the
bedrock, and only the dirt close to the bedrock has gold enough to pay
for working. Even then, it is in spots only.
There
were formerly several makers of dry-washing machines in Los Angeles,
but as far as known there is only one now and no information could be
elicited from him. He is making what he calls a "three-man machine,"
weighing about 50 pounds, and costing $50. Most of the men working at
this business make their own dry-washing machines. They are all
"bellows" machines, in which a pulsating pressure of air is forced
through canvas stretched on wire screen, blowing off the fine material
on the canvas and leaving the gold and black sand to be subsequently
panned. Wire screens are first used to take out the coarser gravel and
refuse before the partly concentrated material is placed on the canvas
shaking table. The whole system is one of concentration by air.
The
total output of these dry placers amounts to but a few thousand
dollars annually in California, because the most of the operations are
carried on by individuals in a small way.
DRY AND SILICEOUS ORES.
In
1912, dry and siliceous ores, including true gold ores and precious
metal bearing ores not classed as copper, lead, or zinc ores, produced
$62,119,916 in gold, against $66,369,199 in 1911. States producing over
$1,000,000 in gold from these ores in 1912 ranked as follows: Colorado,
Nevada, California, South Dakota, Alaska, Arizona, Montana, and Utah.
Increased
output from this source was recorded for 1912 from Alaska, Arizona,
California, and South Dakota, and decreases from the other States
mentioned.
The
siliceous ores are in part free-milling (amalgamating), as in Alaska,
California, and Oregon; in part both amalgamating and concentrating,
as in many States; in smaller part simply concentrating ores, as in
parts of Colorado and Arizona; or smelting ores. Tailings both from old
dumps and from present milling are largely reworked by concentration
and subsequent cyanidation. The all-sliming cyanidation method is also
of increasing importance, and crushing is largely by tube mills as well
as by stamp and gyratory mills.
The
loss in tailings from gold mills is being constantly cut down and the
most serious present loss is in tailings from concentrating plants. The
chlorination process is of decreasing relative importance. Smelting is
mainly of concentrates and of siliceous and pyritic ores which are also
valuable as fluxes. Exact figures of relative output by methods will
appear in detail by States in another table.
