‡Ref.: Ransome, F.L. (1922) Ore deposits of the Sierrita Mountains, Pima County, Arizona, in Contributions to Economic Geology (Short Papers and Preliminary Reports), 1921 - Part I.--Metals and Nonmetals except Fuels: U.S. Geological Survey Bulletin 725J: 416-417.
Farnham, L.L., Stewart, L.A., and Delong, C.W. (1961), Manganese Deposits of Eastern Arizona, US Bureau of Mines Information Circular 7990: 119-121.
Keith, Stanton B. (1974), Arizona Bureau of Geology & Mineral Technology, Geological Survey Branch Bull. 189, Index of Mining Properties in Pima County, Arizona: 131 (Table 4).
USGS Palo Alto Ranch Quadrangle topo map.
Arizona Bureau of Mines file data.
MRDS database Dep. ID file #10039629, MRDS ID #M050526; and, Dep. ID #10137910, MAS ID #0040190088; and, Dep. ID #10186411, MAS ID #0040190460.
A former small surface and underground Pb-Ag-Mn-Cu-Au-Mo mine group located on 22 contiguous unpatented claims, in the SE ¼ sec. 26, and the NE¼ sec. 35, T.17S., R.10E., 7 miles NE of the Palo Alto Ranch and 2 miles NNW of Sunshine Camp. Owned by the Aguinaldo Mining Co. Operated by Mr. Marvin Combs (1969).
Mineralization is veins and replacement lenses of oxidized manganese and sulfides, and wulfenite, in fractured and metamorphosed Paleozoic limestone at or near a contact with granite. Alteration included oxidized Fe and Mn carrying Ag and Pb; fractured and silicified limestone. The host rock unit is the Martin Formation and the Escabrosa Limestone. The ore body is 213.36 meters long, 4.5 meters wide, strikes N-S and dips 45-80E, conformable with the limestone. 3 of the largest Mn occurrences are irregular podlike masses from 2-15 feet wide and 10-50 feet long. They are separated by 100-400 feet of barren or sparsely mineralized limestone.
Local structures include fractured, faulted NNW slivers of Paleozoics; thrust faults. Rocks from the Bisbee group, Continental Granodiorite, and the Pinal Schist are located nearby.
Samples from larger deposits averaged 10% Mn & 10% Fe. High grade ore contained 19-29% Mn & 16-21% Fe. Some ore reported assayed up to 300 oz/t Ag.
Working include adits, shafts, and open cuts to a depth of 76.2 meters. Originally worked for silver prior to 1900, with minor, sporadic, subsequent production occurred 1920-1940, 1942, and 1969. Probably not more than 100 tons of high-grade Pb-Ag ore were produced, plus some Cu and hand-picked wulfenite.
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