Copper World Mine (Helvetia Mine; Black Horse shaft; Brunswick Mine; Little Dave Mine; Owasco Mine), Helvetia, Helvetia-Rosemont District, Santa Rita Mts, Pima Co., Arizona, USA

‡Ref.: Schrader, F.C. & J.M. Hill (1915), Mineral deposits of the Santa Rita and Patagonia Mountains, Arizona, USGS Bull. 582: 92, 99-106.

Creasey, S.C. & G.L. Quick (1955), Copper deposits of part of Helvetia mining district, Pima County, Arizona, USGS Bull. 1027-F: 314.

Galbraith, F.W. & D.J. Brennan (1959), Minerals of Arizona: 82.

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).

Peirce, H. Wesley (1990), Arizona Geological Survey Industrial Minerals card file.

Anthony, J.W., et al (1995), Mineralogy of Arizona, 3rd. ed.: 102, 166, 402.

USGS Sahuarita Quadrangle topo map.

Arizona Bureau of Mines field notes (1971), vol. 1, no. 2.

MRDS database Dep. ID file #10039406, MRDS ID #M050038; and, Dep. ID #10186445, MAS ID #0040190180.

A former small underground Cu-Ag-Au-W-Mo-Wollastonite mine located in the SW ¼ sec. 13 & NW ¼, sec. 24, T.18S., R.15E. on the Brunswick, Owasko, Little Dave & Copper World patented claims, 1¼ miles east of Helvetia, in the upper west slope of the Santa Rita Range at an elevation of about 4,850 feet, 28 miles SE of Tucson. It lies on a N-S ridge between Sycamore Canyon and Helvetia Gulch. Opened in 1900, abandoned, and reopened in 1906. Owned at times, or in part, by the Helvetia Copper Co.; the Michigan Development Co.; Helvetia Copper Co. of Arizona; Mrs. Lon Blankenship, Tucson (1955); and the Santa Rita Mining Co.

Mineralization is copper sulfides, carbonates, oxides and sulfate; and some spotty, disseminated scheelite and molybdenite along fractures, in irregular pyrometasomatic replacements, and disseminated, in silicated and locally pyritized Naco (Pennsylvanian) limestone and underlying Cambrian Bolsa quartzites along a strong fracture zone accompanying a thrust fault plane. This fault dips steeply Eastward at surface and flattens at the depth of the lower mine workings. The Naco has been silicated and generally fractured for a few hundred feet next to the fault. Sulfide minerals occur along fractures, in irregular replacement bodies, and in disseminated grains within the zone of fracture & silication. The majority of copper minerals are probably secondary after chalcopyrite. The limestone is dark and less crystallized near the fractures and thrust. Alteration includes silicification and pyritization of the limestone, narrow oxidized streaks and contact metamorphic minerals.

The ore consists mainly of soft, earthy, fine-grained, mostly pulverulent sulfides (chalcopyrite, cupriferous pyrite and chalcocite), termed "black glance."

Local structures include thrusts and normal faulting, fracture zones, crushed sedimentary rocks and "homocline." No recognizable ore shoots. Large masses of limestone have been completely converted to wollastonite. The Martin Formation, Epitaph Formation, and the Scherrer Formation occur nearby.

Workings include a 200 foot deep single-compartment shaft and a 500 foot deep inclined, 2-compartment shaft, opened in 1900, later in 1906-March 1909, closed in 1910. There were 4 levels. Workings are 152.4 meters deep. There are 4 main levels: 125 feet (135 level), 215 foot level (200 level), 305 foot level (300 level), and the 395 foot level (400 level); 2 sub-levels at 60 feet (100 level) and 160 feet, below the collar of shaft No. 1; a total of 6,540 feet of underground horizontal workings. A major producer, mainly from 1899 to 1916, with some 42,000 tons of ore avareging better than 5%Cu, about 1 oz. Ag/T, and minor Au (4,250,000 pounds of Cu; $1,000 Au; $20,000 Ag). Total production $705,000 (period values)(for 1900-1910?).