Cochise County Arizona Gold Production
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The Tombstone district, about 20 miles northwest of Bisbee in the Tombstone Hills, includes a group of low scattered mountains that extend northwestward from the Mule Mountains. Ores rich in silver were discovered in the Tombstone district in 1877, and the mines and camp developed rapidly. Tombstone produced more than $5 million worth of ore per year in 1881 and 1882, but by 1886 many of the larger ore bodies were either mined out or mined to water level and production decreased sharply, although the district was a steady producer through 1953. During 1879-86 the yield of silver, gold, and lead ore was valued at about $19 million (Butler and others, 1938, p. 38).
By 1900 many of the properties had been combined under one ownership, and an attempt was made to develop the deposits below water level, but this did not prove profitable and was abandoned in 1911 (Butler and others, 1938, p. 38-48). Production was stimulated during World War I and by the increased price of gold in 1934, but from 1948 through 1959 the district was unimportant.
Total gold production through 1959 was about 271,200 ounces, most of which was mined from 1879 through 1932 (Wilson and others, 1934, p. 122).
The oldest rocks in the district are scattered patches of Precambrian Pinal Schist and of albite granite, which are overlain by Paleozoic sedimentary rocks that include the Bolsa Quartzite and Abrigo Limestone of Cambrian .age, the Martin Limestone of Devonian age, the Escabrosa and Horquilla Limestones of Mississippian and Pennsyl-vanian ages respectively, the Earp Formation of Pennsylvanian and Permian age, and the Colina Limestone and Epitaph Dolomite of Permian age. These rocks were folded and faulted in post-Paleozoic pre-Cretaceous time, and then the Bisbee Formation of Cretaceous age was deposited. At the end of Cretaceous time the rocks were cut by thrust faults that trend east and northwest (Gilluly, 1956, p. 128-132). The Uncle Sam Porphyry of early Tertiary age was injected along a thrust, and slightly later the Schieffelin Granodiorite of probable early or middle Tertiary age (Gilluly, 1956, p. 104) intruded the area. Patches of volcanics of Miocene age are exposed to the east of Tombstone. In Pliocene time the rocks were again faulted, this time by great normal faults that are responsible for the present major topographical features (Gilluly, 1956, p. 158-160).
The ore deposits are associated with dikes that are believed to be related to the Schieffelin Granodiorite (Butler and others, 1938, p. 26-28). Ore occurs as replacement bodies in limestones and porphyry, and as fissure fillings. The oxidized ores contain hematite, limonite, cerussite, horn silver, gold and locally abundant argentiferous galena, sphalerite, pyrite, alabandite, malachite, chrysocolla, psilomelane, and wulfenite. Most of the gold occurs as native gold in very fine particles (Wilson and others, 1934, p. 123-124).