Twin Peaks Quarry, Twin Peaks, Amole Mining District, Tucson Mountains, Pima County, Arizona, USAi

Regional Level Types
Twin Peaks Quarry	Quarry
Twin Peaks	Group of Peaks
Amole Mining District	Mining District
Tucson Mountains	Mountain Range
Pima County	County
Arizona	State
USA	Country

A limestone and shale quarry located in South-central sec. 26, T.12S., R.11E, 2 miles NE of Avra. Owned and operated at times, or in part, by the Arizona Portland Cement Co. division of the California Portland Cement Co.

Mineralization is folded and faulted Mississippian Escabrosa, Horquilla Limestone, and Pennsylvanian-Permian Naco Group limestone. The limestone is typically siliceous and contains zones of dolomitic limestone, quartzite, and siltstone. The limestone contains sufficient silica that no additional source of silica is needed for Portland cement production. The Horquilla limestone typically consists of fine-grained, light yellowish gray limestone interbedded with shaley or silty limestone. The Escabrosa limestone consists of white to light gray limestone in the upper and middle parts of the formation and light to dark gray dolomite and limestone in the lower section. The Martin formation consists mostly of very fine- to fine-grained, laminated to thin-bedded, and medium-dark gray to olive-gray dolomite.

Workings include a quarry operation. More than 14,000,000 tons of rock have been mined for cement manufacture.

Material that is too high in silica or more than 6% MgO is crushed, sized, and sold as aggregate. The limestone is used at the Rillito cement plant, which has an annual capacity of 1.1 million tons.
The quarry is 5 miles from the plant, which is at 32-24-49N, 111-08-16W (SEC 5, T12S, R12E). Production capacity is 1.1 million short tons of cement per year. The deposit is selectively mined to produce a low magnesia, controlled-silica limestone.

Other Databases

Link to USGS MRDS:	10060229

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References