Cactus property (Cactus deposit; Pinto shaft; Arizona National Copper shaft; Hamilton shaft), Pinto Creek, Top of the World, Miami-Inspiration District, Globe-Miami District, Gila Co., Arizona, USA

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A relatively small former underground Cu-Mo-Au-Ag-Pb-Zn mine in a disseminated copper deposit located in the E½ sec. 36, T1N, R13E (Inspiration 7.5 minute topo map), on Pinto Creek near the SW corner of the Inspiration Quadrangle, just W of Manitou Hill, about 1½ miles N of Top of the World, on National Forest land. Discovered 1905. Owned by the Cactus Copper Co. (1908- ); and by the Castle Dome Copper Co. (1940). Claims extend into sec. 25, T1N, R13E, and sec. 31, T1N, R14E.

Mineralization is the faulted top of an ore body which dips 40W, hosted in Precambrian Pinal Schist and Gila Conglomerate. An associated rock unit is the Schultze Granite. Ore control was brecciation along the Cactus Fault. Copper carbonates and silicates coat breccia fragments and fill interstices between them. The richest material is just above the fault. Ore concentration was supergene enrichment that possibly took place before thrusting, and oxidation, leaching and deposition during the present erosion cycle. Alteration was hydrithermal with silicification.

This deposit is in a mass of highly shattered and hydrothermally altered Pinal schist that crops out on the north side of Pinto Creek, just west of Manitou Hill. Unaltered, black schist underlies the deposit on the other side of the Cactus fault, which dips 20º to 30º SW. The mineralized schist appears to have been a plate thrust over the normal schist on the fault, probably from the south or SW.

The deposit is gently dipping, partly oxidized chalcocite blanket formed by supergene enrichment. On the west and north sides, its outcrop is overlapped by dacite and Gila conglomerate. The south boundary is formed by the Kelly fault along which the altered schist has been dropped into contact with an unaltered, coarse-grained, quartz-sericite schist, Precambrian granite, and diabase in the south, or footwall, side of the fault. The chalcocite deposit is overlain by 100 to 300 feet of highly silicified schist from which all but a trace of copper has been leached.

The eastern boundary between mineralized and unmineralized schist is marked by a zone of intense brecciation, that probably is the outcrop of the Cactus fault.

The rock that forms the cactus deposit is reported to contain chalcocite, a little pyrite, and copper carbonates and silicates.

Workings include the Pinto and Hamilton shafts, plus 6,500 feet of lateral workings on the 300, 400 and 500 levels of the Hamilton shaft; plus churn drill holes. Workings total 1981.2 meters in length and 152.4 meters in depth. Underground workings are now inaccessible. Taken over by the Pinto Valley Co. in 1921. Work was discontinued in 1929 and not resumed. In 1940 the property was acquired by the Castle Dome Copper Co. Reported to have produced in the early years but no figures are available. This deposit is too small and too low-grade for further exploration.

References

Arizona Mining Journal (1922), February 1, 1922: 19.

Peterson, N.P. (1962), Geology and ore deposits of the Globe-Miami District, Arizona, USGS PP 342: 95-97, 139.

Niemuth, N.J. & K.A. Phillips (1992), Copper Oxide Resources, Arizona Department of Mines & Mineral Resources Open File Report 92-10: 7 (Table 1).

Arizona Bureau of Mines Castle Dome Copper Company Cities Service active file.

Yale Peabody GNIS database (NOTE: this database is derived from USGS 1:24,000 topographic map data).

MRDS database Dep. ID #10027097, MRDS ID #M002008; and Dep. ID #10283049, MAS ID #0040070210.

Mineral List

Chalcocite

Limonite

Muscovite var: Sericite

Pyrite

4 entries listed. 2 valid minerals.