Alta Mine, Hardshell Gulch, Harshaw, Harshaw Mining District, Patagonia Mountains, Santa Cruz County, Arizona, USAi

Regional Level Types
Alta Mine	Mine
Hardshell Gulch	Gulch
Harshaw	- not defined -
Harshaw Mining District	Mining District
Patagonia Mountains	Mountain Range
Santa Cruz County	County
Arizona	State
USA	Country

‡Ref.: The Resources of Arizona - A Manual of Reliable Information Concerning the Territory, compiled by Patrick Hamilton (1881), Scottsdale, AZ: 42-43.

Schrader, F.C. & J.M. Hill (1915), Mineral deposits of the Santa Rita and Patagonia Mountains, Arizona, USGS Bull. 582: 271-272.

Mineralogy of Useful Minerals in Arizona, University of Arizona Bull. 41 (1916-17): 58.

Schrader, F.C. (1917), The geologic distribution and genesis of the metals in the Santa Rita-Patagonia Mountains, Arizona, Economic Geology: 12: 237-269.

Galbraith, F.W. (1947), Minerals of Arizona, Arizona Bureau of Mines Bull. 153: 26.

Galbraith, F.W. & Brennan (1959), Minerals of Arizona: 44.

Baker (1962).

Moores, R.C., III (1972) The geology and ore deposits of a portion of the Harshaw district, Santa Cruz County, Arizona: Tucson, University of Arizona, M.S. thesis, 98 p.: 73.

Simons, F.S. (1972) Mesozoic stratigraphy of the Patagonia Mountains and adjoining areas, Santa Cruz County, Arizona, in Mesozoic stratigraphy in southeastern Arizona: U.S. Geological Survey Professional Paper 658-E.

Simons, F.S. (1974) Geologic map and sections of the Nogales and Lochiel quadrangles, Santa Cruz County, Arizona: U.S. Geological Survey Miscellaneous Investigations Series Map I-762, 9 p., 1 sheet, scale 1:48,000.

Keith, Stanton B. (1975), Arizona Bureau of Mines Bull. 191, Index of Mining Properties in Santa Cruz County Arizona: 56.

Phillips, K.A. (1987), Arizona Industrial Minerals, 2nd. Edition, Arizona Department of Mines & Minerals Mineral Report 4, 185 pp.

U.S. Bureau of Mines staff (1994) U.S. Bureau of Mines Open File Report MLA XX-94.

Anthony, J.W., et al (1995), Mineralogy of Arizona, 3rd.ed.: 224, 340, 393.

Arizona Bureau of Mines file data.

MRDS database Dep. ID file #10048359, MRDS ID #M899948; and, Dep. ID #10210677, MAS ID #0040230015.

A former small underground Pb-Ag-Zn-Cu-Au-Mn-Fluorspar mine located in the center of sec. 4, T.23S., R.16E., 1/3 mile NNW of the Hardshell mine, in the mouth of a southwestern tributary of Hardshell Gulch, at an elevation of about 5,050 feet, 6 miles E of Patagonia, on private (patented) land. Discovered 1875. Worked intermittently in 1877 & 1878, in the 1880's and a little in the 1900's; closed in 1952. Owned/operated by the Melba Mining Co. (1897-circa 1915)(acquired property in 1897 and worked it for a few years).

Mineralization is narrow, spotty, and lensing ore shoots of argentiferous galena, other sulfides, specularite and ruby silver in a fault-fissure vein and wall rock breccia in Jurassic-Triassic rhyolitic volcanics. Mineralization occurs along the hanging wall side of a rhyolite dike emplaced in a fault fissure. The lensing ore shoots are at greater depths. The ore zone is 402.34 meters long with a dip of 40NNE. Gangue is quartz and reddish colored fluorite. Minor amounts of Chalcopyrite. High-grade silver halides in the oxidized surface zone. Alteration includes quartz-fluorite gouge replacements of rhyolite. Surface oxidation exists to unknown depths.

Country rock is the dark-reddish, medium-grained quartz diorite or quartz monzonite, that is cut by a 20 foot dike of light bluish-gray, flow-banded rhyolite breccia at the mine. This dike, as seen in the gulch on the east, is heavily bedded, dips 40ºNNE, and weathers yellowish-brown with limonite stain.

The deposits are obviously associated in origin with the rhyolite dike and seem to occur in its hanging wall side or in the adjoining portion of the wall rock diorite, which is silicified and mineralized for 200 feet back from the dike. Horizontally the lode seems to extend for at least ¼ mile westward. The rhyolite dike dips 40 NNE, and weathers yellowish brown with limonite stain. The rhyolite is locally much altered to sericite, epidote, carbonate, and chlorite.

The argentiferous galena is the principal ore mineral, contained in a gangue of quartz and reddish fluorite, mostly replacing rhyolite.

Local structures include 300 to 400 foot thick lava flows of Hardshell-Hardshaw Creek area. Normal faulting. Slickensides indicate post-vein movement.

Tectonic elements include the Corral Canyon Falt Block with downthrow to the SW.

Workings include an inclined shaft several hundred feet deep. Developed to 300 feet or more by shafts and drifts Worked intermittently in the late 1870's, early 1880's, and to a minor degree into the 1900's. Overall workings total 1219.2 meters in length and 91.44 meters in depth. Developments included a shaft inclined to the N (shaft presently caved in and workings are inaccessible). Workings at 250 feet exposed a 45 foot long, 3 foot wide ore shoot of lead; workings at 300 feet exposed a 4 inch vein of pyrargyrite.

Estimated production is some 3,500 tons of ore averaging about 35% lead, 10 oz. Ag/T, 1% copper and minor gold (17,500 OZ. AG; 2,590,000 LBS PB). At 250 feet depth, a high-grade ore body 2-3 feet wide contains values of 37% Pb with 2 oz. Au, 1% Cu, and 15 oz/ton Ag.

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Link to USGS MRDS:	10048359

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