PLACERS. GENERAL.
The
total value of the gold produced from placers was $15,673,424 in 1918,
against $21,210,587 in 1917. The placer production in Alaska decreased
by 189,146 ounces and that in California by 59,755 ounces. These large
decreases were due to the scarcity of labor, high cost of supplies, and
a shortage of water. The decrease in placer gold from Colorado was
6,522 ounces; from Montana, 3,426 ounces; from Nevada, 3,590 ounces;
from Oregon, 11,084 ounces. The only State showing a considerable
increase in gold produced from placers was Idaho, the increase being
6,830 ounces.
The
placer production is derived chiefly from dredging, 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, often 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 restrictive laws relative to the debris and to
disturbance of navigable streams have in recent years greatly confined
mining activity of this kind. Finally, there is a small annual output
of gold from dry placers in the Southwest and also a production 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 can still be
had on application to the Director, United States Geological Survey,
Washington, D. C.
DREDGING.
The
production of gold by dredging in the United States and Alaska from the
commercial beginning of the industry in 1896 to the end of 1918 has
amounted in value according to best available data to $142,995,832, of
which $102,625,912 came from California', $19,034,894 from Alaska,
$8,843,938 from Montana, $5,273,840 from Colorado, and $3,931,264 from
Idaho. Oregon produced more gold from dredging in 1916, 1917, and 1918
than Montana or Idaho and nearly as much as Colorado, and the total
production from dredges in Oregon has been about $2,900,000.
Brief
details of dredging operations have been given in Mineral Resources in
the mines reports on gold, silver, copper, lead, and zinc of the
Western States and also in earlier reports of the Director of the Mint.
A brief history of gold dredging in the United States was given in the
gold and silver (general) report for the year 1914, and the production
of gold obtained by dredging in the United States and Alaska from 1896
to the end of 1914 and the number of dredges operated was given by
States for each year. Further information is to be found in reports of
geological surveys or mining officials of different States. A
comprehensive and very useful report is contained in Bulletin 57 of the
California State Mining Bureau, "Gold dredging in California," by W. B.
Winston and Charles Janin. Other valuable treatises are "Dredging for
gold in California," by DArcy
