Latitude: 31°52'32"N
Longitude: 110°47'35"W
‡Ref.: Schrader, F.C. & J.M. Hill (1915), Mineral deposits of the Santa Rita and Patagonia Mountains, Arizona, USGS Bull. 582: 132-134.
Dunham, M.S. (1937) Geology of the Blue Jay mine area, Helvetia, Arizona: Tucson, University of Arizona, M.S. thesis, 43 p.
Drewes, H.D. (1971) Geologic map of the Sahuarita quadrangle, southeast of Tucson, Pima County, Arizona: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-613, 1 sheet, scale 1:48,000.
Keith, Stanton B. (1974), Arizona Bureau of Geology & Mineral Technology, Geological Survey Branch Bull. 189, Index of Mining Properties in Pima County, Arizona: 124 (Table 4).
Arizona Bureau of Mines field notes (1971): vol. 1, No. 2.
MRDS database Dep. ID file #10039400, MRDS ID #M050030.
A former small underground Ag-Au-Pb-Cu-W mine located in West-central sec. 12, T.18S., R.15E., 2 miles north of Helvetia, 12 miles south of Vail, and 28 miles SE of Tucson, on a northwest spur of the Santa Rita Mountains, in the south fork of Sycamore Canyon, at an elevation of 4,400 feet, on private land. It is in the south side of the canyon, in a northward-sloping hill. It is Discovered in 1881. First produced 1881. Owned at times, or in part, by the Iowa Mining & Development Co. of cedar Rapids Iowa (1882-circa 1915); the Good Friday Mining Co.; Corzelius; and, Taggert & Drunzer.
Mineralization is tabular replacement deposits of sulfides, oxidized near the surface, with rich chlorargyrite and free gold, along steep bedding planes and lamprophyric dikes in Permian limestone bordering Laramide intrusive quartz monzonite. Ore control was permiable fracture zones. Some copper staining and scheelite in the area. The ore body strikes NW and dips 75NE.
Local rock in the mine is principally the dark-blue or black Carboniferous (?) limestone, on or near its contact with intrusive siliceous granite porphyry. The contact trends east, but the limestone dips steeply to the NW and is cut by dikes of dark-greenish lamprophyric greenstone porphyry that dip steeply to the NE and are associated with the veins and ores. Schists and rocks resembling graywacke and arkose, seemingly older than the limes5tone, occur near by in the canyon on the north.
The deposits occur in the dark limestone country rock, to which they seem to be restricted. They occur principally in two veins or lodes which dip steeply to the NE and are associated with the lamprophyric dikes. The main vein dips about 75º NE, but the dip flattens locally with increase in depth. The vein is from 6 to 18 feet in width, averaging about 10 feet. It consists of sulfide-bearing altered limestone or calcareous quartz and in places contains smaller sulfide veins carrying chiefly silver and gold.
Local structures include dikes which appear to follow thrust fault scarp between limestone and underlying granodiorite, homoclinal. Regional trends include tilting and broad open folds in the south and extensive faulting in the north. The granodiorite is 54 (± 2) MY.
Workings include 4 tunnels, several shafts, drifts, crosscuts, stopes, and winzes, aggregating 3,000 feet or more of work, plus open cuts. The main and lowest tunnel is a crosscut. It opens on the NE in limestone at an elevation of 4,380 feet and runs S.54ºW. ¾ of the way through the hill, ending in granite porphyry at 100 feet below the surface and 25 feet beyond the main vein. At a point near the middle of its length a 150-foot winze is sunk to the vein. The remaining 3 tunnels all open on the NW slope of the hill and run southeastward. The lowest is the Pickett tunnel, at an elevation of 4,430 feet. It is on the main vein and is 300 feet long. The Southwest tunnel, at 4,510 feet, is on the Southwest vein and has a length of 150 feet. The Crooked tunnel, at 4,520 feet, follows a lamprophyric dike for a distance of 160 feet and extends through the hill.
The principal shaft is the Wells shaft, located at an elevation of 4,410 feet, or about 60 feet lower than the main crosscut tunnel, and several hundred feet distant horizontally from its face. It is 110 feet deep and about 500 feet of drifts and crosscuts have been run from it.
Worked sporadically from 1881 to 1939, producing some 2,300 tons of ore together with the Good Friday Mine, averaging about 21 oz. Ag/T, 1 oz. Au/T, and minor Pb. High-grade Ag-Au ore in surface cuts. Ore from the discovery cut (30 feet long and 5 feet deep) averaged 800 oz. Ag/T. Anaconda reported the Rosemont-Helvetia intrusive quartz latite as a potential porphyry copper deposit in 1971.
Mineral List
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