Yavapai County Arizona Gold Production
The Black Canyon district is in southeastern Yavapai County between the eastern foothills of the Bradshaw Mountains and the Agua Fria River, at Bumblebee.
The first locations were made probably as early as 1873, but the first record of mineral production was in 1904. The district was active through 1956, with the highest output from 1934 through 1941. Total gold production from 1904 through 1959 was about 46,700 ounces.
A belt about 2 miles wide of Yavapai schist trends northward through the district and is flanked on the east by a narrow mass of diorite and Bradshaw Granite and on the west by Bradshaw Granite. These rocks, which are all of Precambrian age, are overlain in the eastern part of the district by volcanic rocks of Tertiary age (Lindgren, 1926, p. 153).
The gold ore is in Precambrian high-angle veins and in flat veins of a younger age (Lindgren, 1926, p.156-159).
The Precambrian veins contain coarse glassy quartz and small amounts of chalcopyrite, pyrite, galena, sphalerite, and native gold. Aggregates of minute prisms of blue, brown, or colorless tourmaline are associated with the sulfides. The flat veins, which are also found in the Precambrian rocks, consist of quartz with a little pyrite, galena, chalcopyrite, and locally contain sphalerite and proustite. The gold in these veins is probably in the sulfides.
BLACK ROCK DISTRICT
The Black Rock district, about 12 to 15 miles northeast of Wickenburg, was prospected for copper and silver in the 1870's, but according to meager records the deposits were not developed until 1900 or later (Wilson and others, 1934, p. 62-65). Through about 1932 the district is credited with a gold production of $195,000 (9,438 ounces), most of which came from the Gold Bar (O'Brien) mine (Elsing and Heineman, 1936, p. 103). From 1932 through 1955 the district produced 2,754 ounces of gold, of which at least 99 ounces was placer gold. The total through 1959 was about 12,190 ounces.
The principal rocks of the region are schist and granite of Precambrian age, volcanic rocks (chiefly andesite) of Cretaceous (?) and Tertiary age, and local remnants of basalt of Quaternary age (Arizona Bureau of Mines, 1958).
The ore deposit in the Gold Bar mine is a fissure vein consisting of coarse glassy quartz with pyrite and free gold. In the oxidized zone the quartz is cellular; its cavities are filled with hematite and limonite formed from pyrite, which is common in the deeper zones. Gold occurs as fine to medium-coarse particles, both in the quartz and with the iron minerals (Wilson and others, 1934, p. 63-64).