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Helena Mine, Empire Ranch, Helvetia-Rosemont District, Santa Rita Mts, Pima Co., Arizona, USA

Latitude: 31°52'22"N
Longitude: 110°42'31"W
‡Ref.: Schrader, F.C. & J.M. Hill (1915), Mineral deposits of the Santa Rita and Patagonia Mountains, Arizona, USGS Bull. 582: 92, 138-141.

Arizona Bureau of Mines file data.

MRDS database Dep. ID file #10039613, MRDS ID #M050493; and, Dep. ID #10162153, MAS ID #0040190490.

A former small underground Au mine located in sec. 16, T18S, R16E, in the eastern part of the Helvetia district, 5 miles ENE of Helvetia, 1½ miles SE of Mount Fagan, 2 miles west of Davidson Canyon, and a mile north of the Scholefield Ranch, at an elevation of 4,550 feet, in the toe of the long ridge extending southward from Mount Fagan. Discovered in 1894 and owned by the Rosemont Copper Mining & Milling Co. (circa 1915).

Mineralization is deposits which occur in the rhyolite near its contact with the sedimentary rocks. They are contained in 2 or more fissure veins or ledges which dip west. The main vein has a width of about 7 feet and occupies a fault fissure along which the rhyolite has been considerably fractured and crushed. It dips 40º to 60ºW., and the ore shoots pitch to the north. It has a known extent of about 150 feet vertically and about 500 feet horizontally and a reported extension of ½ mile or more to the north of the mine. It consists principally of iron-stained, reddish-brown, or lavender-colored, crushed and silicified rhyolite and quartz. The quartz is mostly dark gray and impure, and much of it has obviously replaced rhyolite. Some of the quartz is milky white or of a greasy luster and shows by its pseudomorphic structure that it has replaced calcite. Near surface the gangue contains white pyrite, seemingly marcasite. The ore is well oxidized.

Country rock is a close-grained reddish Tertiary rhyolite, intrusive into the dark green shale and sandstone, of which it contains inclusions. These rocks are cut by a NE vertical sheeting.

Workings include drifts, inclines, winzes, raises, stopes, and shafts aggregating an estimated 500 feet of workings, mostly comprised within a vertical range of 150 feet and in a north-south belt about 500 feet long. The main drift is about 250 feet long. A winze off this drift is inclined and 40 feet deep. Production unknown. Gold content was about 10 oz./t.

Mineral List

Gold
Marcasite
Pyrite


3 entries listed. 3 valid minerals.

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Copyright © Jolyon Ralph and Ida Chau 1993-2011. Jobs in Arizona, USA Site Map. Locality, mineral & photograph data are the copyright of the individuals who submitted them.Further information contact the Site hosted & developed by Jolyon Ralph. Mindat.org is an online information resource dedicated to providing free mineralogical information to all. Mindat relies on the contributions of hundreds of members and supporters. Mindat does not offer minerals for sale. If you would like to add information to improve the quality of our database, then click here to register. Current server date and time: 1st Jul 2011 22:02:31
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