Yavapai County Arizona Gold Production
The Big Bug district, on the northeast slope of the Bradshaw Mountains, is about 12 miles east-southeast of Prescott. Copper, gold, silver, lead, and zinc are obtained from a variety of ore deposits in the district.
Wilson, Cunningham, and Butler (1934, p. 39) referred to activity at the Big Bug mine as early as 1866, and other properties were producing gold and silver from oxidized ores before 1870. After a period of decline, some mines were reopened in the late 1890's and maintained a small sporadic annual output through 1933. The tempo of mining increased from 1934 through 1959 mainly because of expanded operation of the Iron King mine. Gold placers were highly productive during the 1880's (Wilson, 1952, p. 48-50) and from 1933 through 1942, after which they declined in importance.
Total gold production from 1867 through 1959 was about 627,000 ounces, of which about 42,700 ounces was from placers.
The Yavapai Series, which here consists of inter-layered sedimentary rocks and volcanic tuffs and breccias, was intruded by a variety of Precambrian granitic rocks—gabbro, diorite, granodiorite, and granite—and by dikes of rhyolite porphyry (Lindgren, 1926, p. 126-127; Anderson and Creasey, 1958, pi. 1). Tertiary volcanic rocks younger than the ore deposits locally form a cover.Lindgren (1926, p. 127) recognized four classes of ore deposits in the district; however, the lead-zinc-silver veins of the Iron King mine have yielded the most gold, and the gold vein of the McCabe-Gladstone property has probably been the second largest gold producer.
The Iron King deposit is a system of 12 massive sulfide veins oriented en echelon in a mylonitized shear zone in the Spud Mountain Volcanics of the Precambrian Yavapai Series (Creasey, in Anderson and Creasey, 1958, p. 156-169). The wallrock is so intensely altered by hydrothermal introduction of quartz, sericite, and pyrite that in places the nature of the original rock cannot be determined. Two groups of veins are recognized in the deposit: well-defined massive sulfide veins, from which all but a few tons of the total ore has been mined, and poorly defined veins, chiefly of pyrite, ankerite, and quartz. The massive sulfide veins comprise thin layers of fine-grained pyrite, sphalerite, chalcopyrite, arsenopyrite, galena, and tennantite. Quartz and ankerite are the major gangue minerals. Gold is in the pyrite, and silver is probably in the tennantite.
The McCabe-Gladstone is one of several mines on the 14,000-foot-long Silver Belt-McCabe vein, a mineralized shear zone in the breccia facies of the Spud Mountain Volcanics. Ore occurs as discontinuous lenses or pods of coarsely crystalline drusy masses of sulfides, with numerous open vugs. The mineralogy of the ore is variable. Silver and lead are abundant in the ores at the north end of the vein. Toward the south end the ores are more complex and contain lead, zinc, iron, silver, copper, and gold. The McCabe-Gladstone mine, which is at the south end of the vein, is in ore composed of arsenopyrite, pyrite, chalcopyrite, and quartz. The gold and silver are in the sulfides (Creasey, in Anderson and Creasey, 1958, p. 169-171).