Hermosa Mine, Hermosa group, American Peak, Harshaw District, Patagonia Mts, Santa Cruz Co., Arizona, USA
|Latitude & Longitude (WGS84):||31° 27' 22'' North , 110° 42' 33'' West|
|Latitude & Longitude (decimal):||31.45611,-110.70917|
|Köppen climate type:||BSk : Cold semi-arid (steppe) climate|
|Other regions containing this locality:||Sonoran Desert, North America|
‡Ref.: The Resources of Arizona - A Manual of Reliable Information Concerning the Territory, compiled by Patrick Hamilton (1881), Scottsdale, Arizona: 42.
Schrader, F.C. & J.M. Hill (1915), Mineral deposits of the Santa Rita and Patagonia Mountains, Arizona, USGS Bull. 582: 272-274.
Schrader, F.C. (1917), The geologic distribution and genesis of the metals in the Santa Rita-Patagonia Mountains, Arizona, Economic Geology: 12: 237-269.
Elsing, M.J. and Heineman, E.S. (1936) Arizona Metal Production, Arizona Bureau of Mines Bulletin 140.
Galbraith, F.W. & D.J. Brennan (1959), Minerals of Arizona: 31, 32, 42.
Moores (1972); Arizona Bureau of Mines file data.
Keith, Stanton B. (1975), Arizona Bureau of Mines Bull. 191, Index of Mining Properties in Santa Cruz County Arizona: 58 (Table 4).
Anthony, J.W., et al (1995), Mineralogy of Arizona, 3rd.ed.: 170, 343, 417.
Keith, S.B., Arizona Bureau of Geology and Mineral Technology file data.
MRDS database Dep. ID file #10037094, MRDS ID #M030389.
A former small underground Ag-Mn-Pb-Cu-Au-Mo mine located in the SE ¼ sec. 4, T.23S., R.16E., about ¾ mile south of Harshaw, and 1/3 mile SE of the Hardshell Mine, in the easterly slope of the same ridge, at an elevation of 5,000 to 5,500 feet, on National Forest land. Located initially in 1877. Produced 1878 - 1950. Owned at times, or in part, by the Hermosa Mining Co., New York (later the Prietus Mines Co.) (1878 or 1879; October 1880-November 1881); Mr. James Finley, of Tucson (1887-circa 1891; 1892); Senator McGoverney, of Canon City (1891); Hermosa Mining & Milling Co., of Guthrie, OK (circa 1892-circa 1902); Mr. James Cochran, of Bradford, PA (1906-circa 1915); A.R. BYRD (1941); E. Bolinger; and, Mr. Grover Marsteller (1950). Located incorrectly by USGS on topo sheet. It is actually SE of where shown.
Mineralization is irregular, tabular, oxidized quartz-lode (1 to 12 feet wide and dips 33ºN.) with high-grade pockets of chlorargyrite and other silver chlorides in fracture fillings and replacements of Jurassic rhyolite and latite porphyry breccia along a fault zone. Considerable iron and manganese, and minor molybdenum staining of wall rocks and quartz. Weak oxidized base metal mineralization. Ore concentration was metasomatic replacement in the altered, partially silicified rhyolite gangue. Depositing solutions dissolved out of less resistant wall rock.
Country rock is an ash-gray rhyolite which is mainly breccia and is locally called by miners from Colorado "Cripple Creek breccia." It is crushed, recemented, and locally closely banded by flow structure. It is also secondarily banded, largely with quartz, and is more or less altered, stained dark reddish or yellowish-brown by iron, and mineralized. It is practically all oxidized, no pyrite or sulphide being found at any point.
A subordinate lode, the North vein, parallels the main lode at a distance of 50 feet on the north at the surface. It has a steeper dip.
The ore mineral is chlorargyrite, and except for a little molybdenite stain and iron and manganese oxides, the ore contains no other metal.
Workings include an inclined shaft and tunnel workings; 5 levels at 50 foot intervals vertically. The mine is developed to a depth of about 500 feet (152.4 meters) below the surface at the top of the ridge by 7,000 feet (2133.6 meters) or more of work, principally drifts, stopes, and tunnels distributed mainly on 5 levels. A winze is sunk 300 feet from the west drift on the tunnel level. The tunnel is 700 feet long. The shaft is about 100 feet below the tunnel; drifts & crosscuts.
Worked from the 1870's to 1900 and in 1908 and 1949-1950. Some 70,000 tons of of better than 20 oz. Ag/T manganese-silver ore was mined and shipped. Largely used as smelter flux. A 20-stamp mill with an 80 tons/day capacity was installed. Total production, mostly as silver chloride amalgamated on the site, was some $1,500,000 of Ag (period values).
4 valid minerals.
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 Macrostrat.org
|Tithonian - Bajocian|
145 - 170.3 Ma
|Jurassic sedimentary and volcanic rocks|
Age: Jurassic (145 - 170.3 Ma)
Description: Sandstone and conglomerate derived from volcanic rocks with associated intermediate-composition lava flows, breccias, and tuffs. In southern Arizona this unit includes rocks of the Artesa sequence, Pitoikam Formation, Mulberry Wash volcanics, Rudolfo Red Beds, Recreation Red Beds, and Gardner Canyon Formation. In western Arizona it includes the Harquar Formation, rocks of Slumgullion, and related(?) unnamed units in the Kofa and Middle Mountains. This unit is characterized by maroon, brown, and purplish-gray volcanic-lithic sandstone and siltstone, with subordinate to abundant conglomerate, quartz-rich sandstone and sparse limestone. (150-170 Ma)
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.