Yavapai County Arizona Gold Production
The Jerome (Verde) district is on the eastern slope of the Black Hills in northeast Yavapai County just west of the Verde River. Both gold and silver have been produced as byproducts of copper mining from the two major mines in this district— the United Verde and the United Verde Extension.
Centuries ago the copper ores at Jerome were utilized by Indians for jewelry and dyes. In 1582 and 1598 Spanish explorers visited the deposits and located claims, though they did not work them. The deposits remained unnoticed and undeveloped until their rediscovery in 1875 by U.S. Army troops. In 1876 prospectors entered the area, and by 1882 the newly organized United Verde Copper Co. began consolidating the numerous claims and later became the largest producer of the district. Oxidized ores rich in gold, silver, and copper were mined in 1883-84, but by the end of 1884 the ore was exhausted and the price of copper dropped, so that work was suspended at the United Verde property until 1888. Prospecting elsewhere in the district in the early 1900's was successful, and for a time several small mines were active. The United Verde Extension Gold, Silver, and Copper Mining Co. was organized in 1899, and under its successors it became the second largest mine of the district. In the early 1900's the United Verde Extension Co. explored extensively, first to the southwest and later east of the prospering United Verde property. Most of these efforts were fruitless; nevertheless, work continued until the company was on the verge of collapse. Finally in 1914, a rich chalcocite ore body was found on the 1,200 level, and in 1916 a much larger ore body was found. The company operated on a large scale until 1938 when the deposit was mined out and the mine was closed.
The United Verde mine continued its underground operations until 1931, after which open-pit mining was the chief activity. Depletion of reserves finally forced the mine to close in 1953 (Anderson and Creasey, 1958, p. 84-90).
The large-scale copper mining yielded a total of about 1,565,000 ounces of byproduct gold from 1883 through 1951 (Anderson and Creasey, 1958, p. 101). Total gold production from 1883 through 1959 was about 1,571,000 ounces.
Most of the central and southern parts of the Jerome district are underlain by slate, phyllite, schist, gneiss, and granulite that make up the Yavapai Series of Precambrian age. These rocks are intruded by numerous irregular bodies of quartz porphyry, gabbro, quartz diorite, and granodiorite, also of Precambrian age. Paleozoic sedimentary rocks, which cover parts of the northern half of the district, overlie the Precambrian rocks unconformably and range in age from Cambrian to Penn-sylvanian or Permian. Rocks of Mesozoic age do not occur in the district; a thick section of lava flows and intercalated sedimentary rocks of Pliocene (?) age and lake deposits of late Pliocene and Pleistocene age overlap the older rocks (Anderson and Creasey, 1958, p. 8-61).
The Precambrian rocks were deformed during several periods of faulting and folding. Later faulting, accompanied by tilting, displaced the Paleozoic and Cenozoic rocks (Anderson and Creasey, 1958, p. 62-83). The important ore deposits of the district are massive sulfide deposits of Precambrian age. At the United Verde mine the main ore body was a pipelike mass of pyrite, chalcopyrite, sphalerite, quartz, and carbonates that replaced quartz porphyry and tuffaceous sedimentary rocks. The deposits of the United Verde Extension mine were buried beneath a cover of Paleozoic and Tertiary sedimentary rocks. Ore consisted of elliptical masses of chalcocite in Precambrian rocks. Massive sulfide, similar in composition to the United Verde ore body, underlies the chalcocite. In both mines the sulfide ore bodies were overlain by oxidized zones containing iron oxides, malachite, azurite, chrysocolla, gold, silver, and native copper (Anderson and Creasey, 1958, p. 103-145).