The
production of gold from placer mining in 1921 was $1,538,676 more than
in 1920. The States showing a considerable increase in
p
lacer gold were Alaska
(17,076 ounces), California (52,932 ounces), Idaho (3,279 ounces),
Nevada (10,183 ounces), and Oregon (1,336 ounces). The only prominent
decreases were in Colorado (8,221 ounces) and Montana (2,989 ounces).
The
placer gold is derived chiefly from dredging (which yielded 75 per cent
of the total in 1921), from drift mining (which is of decreasing
importance in Alaska in frozen ground at no great depth, but of
continued importance in California in ancient buried river channels, in
places at considerable depth), and from hydraulic and sluicing placers.
In California, especially, hydraulic mining was of much importance in
the past and had become a special branch of the industry in itself but
has in recent years been greatly reduced by restrictive laws relative
to the debris and to disturbance of navigable streams. Finally, there
is a small annual output of gold from dry placers in the Southwest and
also of gold and platinum from ocean-beach mining in California and
Oregon.
Some
interesting notes on beach mining in California and Oregon and on dry
placers in California, by Charles G. Yale, and on dry placers in
Arizona, Nevada, and New Mexico, by V. C. Heikes, were published in the
Survey report on gold and silver for 1912, copies of which may still be
had on application to the Director, United States Geological Survey,
Washington, D. C.
