Tombstone Mining District, Cochise County, Arizona, USAi

Regional Level Types
Tombstone Mining District	Mining District
Cochise County	County
Arizona	State
USA	Country

This mining district is located in T20 & 21S, R21 & 22E, G&SRM, in the Tombstone Hills, at an altitude of 4,530 feet (ca. 1,381 m). It is some 25 miles (ca. 40 km) north of the international boundary and about 25 miles (ca. 40 km) NW of Bisbee.

This is a Ag-Au-Pb-Cu-Zn-Mn-Mo-V, mica, clay (As-Cd-Sb-Te) mining area principally famous for its silver mines and located about 20 miles (ca. 32 km) NW of Bisbee. This was the first major mining district discovered in Cochise County once the issue of an Indian reservation was resolved. It was discovered in February 1878, by Mr. A.E. Shieffelin, a daring local prospector. He was warned by the soldiers at Fort Huachuca that wandering in this area would earn him only a tombstone. When he discovered the rich deposits in this area, he named the new camp "Tombstone." Tombstone is at an altitude of 4,500 feet (ca. 1,372 m) on a gravel-floored pediment at the northern margin of a small group of low, dissected mountains, called the Tombstone Hills, that attain an altitude of about 5,300 feet (ca. 1,615 m). The Tombstone District is in southwestern Cochise County, 20 miles (ca. 32 km) NW of Bisbee. From 1879 to 1932, this district produced more than 29,843,800 ounces (ca. 1,128 t) of silver, 35,669,800 pounds (ca. 16,180 t) of lead and $5,127,300 of gold (period values), besides considerable copper, zinc, and manganese.

As interpreted by Ransome, the basement rocks are fine-grained Pinal Schist with intruded gneissic granite, which outcrop in a small area south of the principal mines. The unconformably overlying Paleozoic quartzite and limestones have a total thickness of 4,000 to 5,000 feet (ca. 1,524 m), with 2,500 to 3,500 feet (ca. 1,067 m) of Mississippian Escabrosa and Pennsylvanian Naco limestones as their upper formations. Unconformably overlying the Naco Limestone is a Mesozoic series of conglomerate, thick-bedded quartzites, and shales, with two or three lenses of soft, bluish-gray limestone. These formations are intruded by large bodies of quartz monzonite and by dikes of quartz monzonite-porphyry and diorite-porphyry. The region is complexly faulted, and, particularly, just south of Tombstone, the strata are closely folded.

The ores of the Tombstone District occur in at least three ways: (1) As argentiferous lead sulfide with spotty copper and zinc minerals, usually deeply oxidized with enrichment in irregular replacement bodies along fissure zones and anticlinal rolls cut by mineralized fissures in Paleozoic and Mesozoic sedimentary formations. Orebodies are often closely associated with cross-cutting Laramide intrusive dikes; (2) Base metal mineralization, often oxidized, in fault and fracture zones in Laramide volcanics and quartz latite porphyry intrusive; (3) Manganese oxides, argentiferous at times, in irregular, lenticular or pipe-like replacement bodies along fracture and fault zones, typically in Pennsylvanian-Permian Naco Group limestones.

Workings are numerous shaft mines and prospects. Total production of lead and silver ore has been at least 1.5 million tons since 1878. About 9,000 tons of manganese ore and concentrates have also been produced for smelter flux and for manganese.

Production from 1879 through 1936 was some $37,103,008 (period values).

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References