Yuma County Arizona Gold Production
The Cienega district is in northwestern Yuma County, 5 to 8 miles northeast of Parker.
Some mining was done as early as 1870 (Wilson and others, 1934, p. 126). Gold-copper lodes developed during 1909-20 had small sporadic yields. Intermittent activity continued through 1957.
Nolan (in Hewett and others, 1936, p. 31) estimated that the district produced ore worth $80,000 (chiefly in gold) before 1908, but Elsing and Heineman (1936, p. 104) credited the district with $415,000 (about 20,000 ounces), from 1870 to 1933, most of which must have been mined before 1908 because recorded production from 1908 to 1933 was only 4,271 ounces. Total gold production through 1959 was at least 10,000 ounces.
A thick section of Paleozoic metamorphosed sedimentary rocks, consisting of limestone, shale, and quartzite, is the predominant bedrock in the district. These rocks are cut by intrusive bodies of granite and are overlain locally by basalt. Gold, chrysocolla, malachite, limonite, and specularite occur in brecciated pockets of sedimentary rock along shear zones.
The Dome (Gila City) district is at the north end of the Gila Mountains, about 15 miles east of Yuma.
Discovered in 1858, this placer district attracted a horde of prospectors who worked the rich gravels of Monitor Gulch and other gulches and benches near the newly founded settlement of Gila City, just west of the present town of Dome (Wilson, 1952, p. 18-19). By 1865 the high-grade placers were worked out, but spasmodic activity continued to 1950. Total gold production through 1959 was about 24,765 ounces, the bulk of which was mined before 1865.
ELLSWORTH DISTRICT
The Ellsworth (Harquahala) district is in the Little Harquahala Mountains, 5 to 10 miles south of Salome.
Small placer deposits in Harquahala Gulch were worked in 1886 and 1887, and the lodes of the Bonanza and Golden Eagle mines, from which most of the gold of the district has been mined, were found in 1888. The period of greatest activity was from 1891 to 1897, after which the ore bodies were considered to be worked out (Wilson and others, 1934, p. 128). Small production by lessees continued at intervals through 1957. Total gold production of the district through 1959 was about 134,000 ounces; nearly all production was from lodes.
Granite, of probable Precambrian age, is overlain by schist, quartzite, shale, and limestone, some of which may be as young as Carboniferous (Dar-ton, 1925, p. 221-223). Gold-bearing quartz veins are along shear zones in the sedimentary rocks and granite. The oxidized ores contain much free-milling gold; the sulfide ores, mined in more recent years, contain pyrite, galena, and local covellite (Bancroft, 1911, p. 106-114).