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Montosa Mine (Montosa group of claims), Montosa Canyon, Tyndall District, Santa Rita Mts, Santa Cruz Co., Arizona, USA

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Latitude & Longitude (WGS84): 31° 40' 7'' North , 110° 55' 45'' West
Latitude & Longitude (decimal): 31.6686111111, -110.929166667
Other regions containing this locality:Sonoran Desert, North America

‡Ref.: Schrader, F.C. & J.M. Hill (1915), Mineral deposits of the Santa Rita and Patagonia Mountains, Arizona, USGS Bull. 582: 186-187.

Anthony, J.W. (1951) Geology of the Montosa-Cottonwood Canyons Area, Santa Cruz County, Arizona: Tucson, Unitversity of Arizona, M.S. thesis, 84 p.

Sulik, J.F. (1957) Stratigraphy and structure of the Montosa Canyon area, Santa Cruz County, Arizona: Tucson, University of the Arizona, M.S. thesis, 64 p.

Keith, Stanton B. (1975), Arizona Bureau of Mines Bull. 191, Index of Mining Properties in Santa Cruz County Arizona: 86 (Table 4).

Arizona Bureau of Mines file data.

MRDS database Dep. ID file #10137904, MAS ID #0040230292.

A former underrgound Pb-Ag-Cu-Zn-Au mine on a group of 14 claims located in the NE¼ sec. 28 & the NW¼ sec. 29, T.20S., R.14E., southwesterly part of Montosa Basin and adjoining hills, at an elevation of about 4,900 feet, on land of mixed status, including patented (private) land. First produced 1901. Owned at times, or in part, by Captain John D. Burgess, of Tucson (circa 1901); Freeman & Smith, of Tucson; the Calabasas Copper Co.; Boykin; Amado Mines; and, McIntosh.

Mineralization is largely oxidized sulfides in an irregular replacement body in a large, exotic Paleozoic limestone block, that dips to the SW, engulfed in Cretaceous dacitic volcanic breccia, and also as spotty mineralization in a quartz-fissure vein cutting the dacite volcanics.

The deposit trends about N.70ºW. and lies in a mineralized zone which extends at least 1/8 mile to the SE and beyond which the limestone soon gives way to the overlying andesite that caps the mountains.

A 30 by 40 foot open cut, the principal surface exposure, is about all in low-grade ore or bedded mineralized material. Some 2,000 feet of underground workings were developed by the Calabasas Copper Co., Ltd. of New York, mostly on the Isabella ground. Shaft(s) were sunk to 250 feet. The ore carried about 360 oz. Ag/T and 3.1 oz. Au/T.

Worked sporadically from the early 1900's through 1949. The group produced some 1,000 tons of ore averaging about 22% Pb, 3% Cu, 3 oz. Ag/T and minor Zn and Au.

Mineral List

Mineral list contains entries from the region specified including sub-localities

12 valid minerals.

Regional Geology

This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.

Click on geological units on the map for more information. Click here to view full-screen map on

Ypresian - Campanian
47.8 - 83.6 Ma
Early Tertiary to Late Cretaceous volcanic rocks

Age: Phanerozoic (47.8 - 83.6 Ma)

Stratigraphic Name: Williamson Canyon Volcanics

Description: Rhyolite to andesite and closely associated sedimentary and near-surface intrusive rocks; commonly dark gray to dark greenish gray or greenish brown. In the ranges west of Tucson, this unit includes thick welded ash-flow tuffs. Volcanic rocks of this unit are inferred to be derived from vents and volcanoes above magma chambers that solidified to form the granitic rocks of map unit TKg. These rocks are restricted to southeastern Arizona except for a small outcrop near Bagdad. (50-82 Ma)

Comments: Related, broadly, to unit TKg

Lithology: Major:{rhyolite,dacite,andesite}, Minor:{clastic}

Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052. [133]

Data and map coding provided by, used under Creative Commons Attribution 4.0 License

Localities in this Region


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