Location
East side of the Dome Rock Mountains, Tps. 3 and 4 N., R. 20 W.
Topographic Map
Dome Rock Mountains 15-minute quadrangle.
Geologic Map
Wilson, 1960, Geologic map of Yuma County, Arizona, scale 1:375,000.
Access
From Quartzsite it is about 5 miles west on U.S. Highway 60-70 to Dome Rock Mountains. Dirt roads lead from the highway to adjacent placers.
Extent
Placers are found on the east side of the Dome Rock Mountains in three localities: La Cholla placers, located south of U.S. Highway 60-70 in an area 4 to 5 miles long from east to west (NEJ4 T. 3 N., R. 20 W.); at the southern base of the Middle Camp Mountain (approximately SW14 T. 4 N., R. 20 W., unsurveyed); Oro Fino placers, located north of U.S. Highway 60-70 and southeast of the Middle Camp placers (SE14 T. 4 N., R. 20 W., unsurveyed).
Production History
The placers on the east side of the Dome Rock Mountains have been worked intermittently since the 1860's. The placer camps are usually considered to be part of the Plomosa mining district and production records are usually grouped with the Plomosa placers, 12 miles east. The deposits at La Cholla and Middle Camp have been worked on a small scale throughout this century.
From the 1930's until 1941, the La Cholla placers were the most active in the area; large-scale operations by the La Posa Development Co. at the Arizona Drift mine during the period 1939- 41 accounted for most of the placer production. This company worked a channel on bedrock that was 6 feet thick and 50-150 feet wide at a depth of 140 feet. No estimates of the average value of the gravels worked by this operation have been found, but the gravels worked in an earlier operation contained in places as much as 1 ounce of gold per cubic yard, and the tailings were valued at 85 cents per cubic yard.
Source
Gold-quartz veins in the mountains immediately adjoining the placer deposits are the source of the placer gold.
Literature
Allen, 1922: Quotes Heikes and Yale (1913).
Berger, 1932: Placer-mining techniques and operations at La Cholla.
Gardner and Johnson, 1935: Depth of gravels; width of gold-bearing channel; placer-mining operations.
Heikes and Yale, 1913: Location; types of gravel at different localities; size of nuggets; past placer-mining history.
Jones, 1915: Placer-mining operations at Oro Fino; gold values in gravels.
Mining Journal, 1939a: Operations by La Posa Development Co., number of men employed; yards of gravel mined per day; equipment used; thickness of pay gravel; width of channel.
U.S. Bureau of Mines, 1940: Reports cubic yards of gravel mined at La Cholla placers in 1939.
Wilson, 1961: Location; placer-mining activity; distribution of goldbearing gravels.
