PINOS ALTOS DISTRICT
The Pinos Altos district is about 8 miles northeast of Silver City in the Pinos Altos Mountains. Both placer and lode gold were discovered in 1860, and within 2 years about 30 lode mines were being worked. The Civil War and the postwar depredations of Apache Indians brought about almost complete abandonment of the camp for several years (Lindgren and others, 1910, p. 297). In 1867, operations were resumed and they continued with brief interruptions until the late 1950's. Gold was the principal product in the early years. Silver, copper, and lead later gained significance, and after 1912, zinc was of major importance.
Gold production in ounces is summarized in the following table:
The most productive placer deposits were found along Bear Creek Gulch, Rich Gulch, Whiskey Gulch, and unnamed gulches near the old Gillette shaft. The principal lode mines are on the east side of the Pinos Altos Mountains; a few are on the upper western slope.
The Pinos Altos Mountains consist of eastward-tilted and faulted limestone of Pennsylvanian age, Cretaceous quartzite, shale, and andesite breccia. These rocks are intruded by hundreds of mafic dikes, and by masses of diorite and granodiorite of Late Cretaceous or early Tertiary age. North of the Pinos Altos district the sedimentary and intrusive rocks are covered by younger Tertiary tuff (Paige, 1911, p. 109-125).
The lode deposits are of two types: veins in igneous rocks and replacement deposits in the limestone.
The veins range in length from a few hundred feet to nearly a mile and have an average width of 2% feet. The ore minerals are pyrite, sphalerite, galena, and chalcopyrite. Quartz is the principal gangue, but calcite, barite, and rhodochrosite are locally present. Gold and silver are present in all the veins.
The replacement deposits occur at two distinct horizons in the limestone, 4 to 15 feet apart. The ore consists of intimately intergrown sphalerite, chalcopyrite, pyrite, quartz, and carbonate minerals. Zinc, copper, silver, and small amounts of gold are recovered from these ores (Paige, 1911, p. 113-125).
STEEPLE ROCK DISTRICT
The Steeple Rock district is in western Grant County, about 4 miles from the New Mexico-Arizona boundary. Shortly after the initial discoveries in 1880, the Carlisle mine was developed and by 1897 its production was valued at about $3 million in gold and silver (Graton, in Lindgren and others, 1910, p. 327). Production figures from 1897 through 1931 are not available, and although ore was shipped, the total production is believed to have been small (Anderson, 1957, p. 76). A fairly prosperous interval began in 1932 and lasted through 1955. During this period 34,050 ounces of gold, in addition to considerable silver, copper, lead, and zinc, was produced. The district was idle from 1956 through 1959.
The rocks in the district are lavas of Tertiary age and range in composition from soda rhyolite to diorite. Quartz, accompanied by small amounts of calcite, is the predominant gangue mineral. Pyrite, sphalerite, chalcopyrite, and galena are the ore minerals.
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