Eclipse Mine group, 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: 118.

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: 125 (Table 4).

USGS Sahuarita Quadrangle topo map.

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

MRDS database Dep. ID file #10039407, MRDS ID #M050040; and, Dep. ID #10162233, MAS ID #0040190201.

A former small underground Cu-Pb-Ag-Au-Mo-Zn mine group of three claims (1 patented, 2 unpatented) located in South-central sec. 24 & North-central sec. 25, T.18S., R.15E, 28 miles SE of Tucson. This group of claims lies on the rugged crest of the range at an elevation of about 5,000 feet, between the helvetia properties on the west and the Rosemont properties on the east. Owned by G.E. Dunbar of Kalamazoo, Michigan (circa 1915); and, Steinfeld & Co.

Mineralization is irregular ferruginous gossan zone with copper and lead carbonates underlain locally by disseminated and massive chalcocite and argentiferous galena in pyrometasomatic replacement deposits along a faulted contact. The contact is upfaulted cupriferous Paleozoic quartzite on the west and the overlying silicated limestone on the east, in thrust-faulted block segments. This contact is known as the 'second contact.' The limestone along the contact is well-mineralized for a width of 20 feet or more and contains the metals indicated in the croppings by a ferruginous copper carbonate gossan or iron cap. The impervious quartzite footwall was seemingly an important physical factor in the concentration of the ore. Host rock units are the Concha Limestone (cherty limestone), the Scherrer Formation and quartzitic sandstone. An associated rock unit is quartz latite (56 ± 2MY). Alteration included gossan and skarn. The ore is 45.72 meters depth to bottom and 11.28 meters thick.

Local structures include thrust and normal faulting, fracture zones, homoclinal. Regional trends include tilting and broad open folds in the south and extensive faulting in the north.

Workings included a shaft. Production was prior to 1900, years estimated.