By A. H. KOSCHMANN and M. H. BERGENDAHL - USGS 1968
Maricopa County, in southwestern Arizona, is a region of broad desert plains and scattered mountain ranges. Most of the gold was mined in the county before 1900 from the Vulture mine in the Vulture district. The Cave Creek district has yielded a small amount of gold. Maricopa County is the fifth largest gold producer of Arizona, and from 1863 through 1959 its total production was about 428,000 ounces. Most of this was from lode mines; only about 3,000 ounces was attributed to placers.
CAVE CREEK DISTRICT
The Cave Creek district, 25 to 45 miles north of Phoenix, was active at least as early as the 1890's, when the Phoenix and Maricopa mines were the major properties and were yielding gold ore. A few copper deposits were also worked before 1900 (Wilson and others, 1934, p. 164-165). Total gold production of the district through 1959 was about 17,000 ounces, most of which was mined before 1900.
The Vulture district is on the south side of the Vulture Mountains, in northwestern Maricopa County.
Gold-bearing quartz veins were discovered in 1863. In 1866 the Vulture mine began operations that continued on a fairly large scale until it was closed in 1888. The mine was active again from 1910 to 1917, during which time it yielded $1,839,375 in ore (Wilson and others, 1934, p. 157, 160). The mine was reopened again in 1931 and remained active until 1945. Total gold production for the district through 1959 was about 366,000 ounces. About 250 ounces of this was from placers; most of the remainder was from the Vulture mine.
The Vulture Mountains are faulted andesitic and rhyolitic lavas of Tertiary age. These rocks overlie Precambrian schist and granite which are intruded by monzonite dikes of probable Mesozoic age. The ore deposits are in veins in the schist (Wilson, 1952, p. 58). The veins are chiefly coarse quartz with pyrite, galena, sphalerite, chalcopyrite, and native gold. Gold also occurs in the galena, and Hutchinson (1921) reported that clean galena concentrates assayed $600 per ton in gold.