insufficient
quantity to be depended upon to assist in present economical
extraction by hydraulic methods used elsewhere in recovery of placer
gold. In earlier years the Sonora district in Mexico undoubtedly
produced much gold from the loose surface gravels, mainly by simple pneumatic concentration in bateas and Hungarian "dry washers," operated by hand.
It
seems probable that further production of gold can be expected from
some of these dry placers, but whether at a profit to operators and
investors or not will depend upon thorough understanding of the
conditions, and technical and financial management not only honest but
efficient and economical as well. Costly and financially unprofitable
experiments have been reported in attempts at recovery of gold by "dry
washing" of some of these deposits, and intending investors might
profitably consult the literature already available on the subject.
Detailed information relative to the geology and occurrence of this
dry-gravel gold in the southwestern United States is still largely
lacking.
Recent Survey publications giving some information on dry placer gold in the Southwest are papers by Hill,1 Hess;2 and Lindgren, Gra-ton, and Gordon,3
and the chapters on New Mexico, Arizona, Utah, and California in the
annual reports of the Survey, "Gold, silver, copper, lead, and zinc in
the Western States (mine production)," published as advance chapters
and also in the volumes "Mineral resources of the United States." All
of these papers can be had free on application to the Director, United
States Geological Survey, Washington, D. C, until the Survey stock is
exhausted, and after that on payment of cost of publication to the
Superintendent of Documents, Washington, D. C. As the recovery or gold
from dry gravels has been the subject of many inquiries to the Survey
the following list of recent references to the literature is given.
Copies of these papers can in most cases probably be had at small cost
from publishers of the leading mining journals.
Baker, H. D., Placer gold machine: Min. Sci., vol. 64, 1911, p. 538.
Carey, E. E., Working* dry placers: Am. Metall. Soc, vol. 1, 1911, p. 6.
Dolbear,
S. H., Dry placer mining in California: Eng. and Min. Jour., vol. 89,
1910, p. 359. Describes dry placer gravels in Summit region, San
Bernardino County, Cat, and experiments of Jardine and Patton in
recovery of gold.
Engineering
and Mining Journal, Dry pulverizer and separator, vol. 89,1910, p. 858.
Describes Qumner dry pulverizer and separator.
---------Special correspondence. The Altar gold placer fields of Sonora, Mexico, vol.
90,
1910, pp. 651-653. Gives history of operations m dry placer mining,
brief descriptions of deposits, and working of Quinner dry pulverizer.
---------Editorial correspondence, vol. 91, 1911. p. 535. Gives notes on probable
working of dry gravels in the Summit region, north of Randsburg, San Bernardino County, Cal.
Ficket,
F. W., Dry placer mining in Quijotoa district (Arizona-Mexico): Min.
and Sci. Press, vol. 102, 1911, p. 291. Describes occurrence of gold in
caliche or lime-cemented conglomerate, and operations of Quinner and Stebbins machines.
Jardine, J. B., jr., Dry concentration of placer gold: Am. Metall. Soc, vol. 1, 1911, p. 21.
Merrill,
F. J. H., Dry placers of northern Sonora, Mexico: Min. and Sci. Press,
vol. 97,1908, pp. 360-361. Describes dry gold gravels of Altar region,
Sonora, Mexico, and Hungarian "dry washer" machine, and briefly states
essentials for successful working of gravels.
1 Hill J. M., Notes on placer deposits of Greaterville, Ariz.: Bull. U. S. Geol. Survey No. 430, 1910, pp. 11-22.
s Hess, F. L., Gold mining in the Randsburg quadrangle, Cal.: Bull. TJ. S. Geol. Survey No. 430, 1910, pp. 23-47.
3
Lindgren, Waldemar, Graton, L. C, and Gordon, C H., The ore deposits of
New Mexico: Prof. Paper U. S. Geol. Survey No. 68, 1910, pp. 74-76.
