Location
Kofa Mountains, T. 2 S., R. 17 W.
Topographic Map
Kofa Butte 15-minute quadrangle.
Geologic Maps
Jones, 1916, Geologic reconnaissance map of the Kofa Mountains, Arizona (pi. 5), scale 1:125,000.
Wilson, 1960, Geologic map of Yuma County, Arizona, scale 1:375,000.
Access
From Yuma, 59 miles east and north on State Highway 95 to dirt road leading east about 15 miles to dirt road leading about 10 miles north to the Kofa Mountains.
Extent
Many gulches in the southern and northeastern part of the Kofa Mountains are said to contain gold-bearing gravels; the only placer area described is in a westward-trending wash just north of the King of Arizona mine (sees. 1 and 12, T. 2 S., R. 17 W.). The gold-bearing debris consists of boulders and fragments of metamorphic and volcanic rocks and ranges in thickness from a few feet to 70 feet. The gold in the gravels is coarse and occurs near bedrock.
Very little information has been found relating to other placers in the Kofa Mountains. An underground placer mine, the Alamo mine, is said to be located in conglomerate and to have high gold values; the Alamo mine might be located near Alamo Spring in the Kofa Mountains (T. 1 N., R. 16 W.).
Production History
The only placer of importance in the area is the deposit north of the King of Arizona mine; the total production to 1914 was estimated at $40,000. During the 20th century small-scale intermittent placer-mining activity has produced small amounts of gold from this area. No production is known from the Alamo mine.
Source
According to Jones (1916), who studied the Kofa placer in detail, the source of the gold was small auriferous veins in the metamorphic rocks exposed north of the placer deposits in sec. 1, T. 2 S., R. 17 W., and not from the King of Arizona mine.
Literature
Allen, 1922: Virtually repeats description of Jones (1916).
Jones, 1916: Location; production; placer-mining activity; thickness of gold-bearing gravel; size and distribution of gold; source.
McConnell, 1911: Alamo placer; gold values in conglomerate.
Wilson, 1933: Quotes Jones (1916), production from 1914 to 1928.
1961: Quotes Jones (1916), placer-mining activity and production per man during the period 1932-33.
