Benton Mine

Not in Keith, 1975.

Alternate Names

None

Company

Dennis Coughlin and partners².

Mining District and Mines

Patagonia District

Arizona Geological Survey Mining data

http://docs.azgs.az.gov/OnlineAccessMineFiles/G-L/JarillasmineSantacruz130A.pdf is not the same mine.

Location

South side of the Patagonia mountains, close to the border.

23S 15E SE¼ 9⁵

31.43931N, 110.80957W⁴

Mineral Products

Ag, Pb, Au-, Cu-, Mo-, Mn-.⁵

Geology

The country rock is quartz monzonite, which is cut by granite porphyry , diorite, and aplitic granite, the two last-named rocks cropping out on the hill above the tunnel. The granite porphyry occurs mainly in a 60-foot north-south dike. It is impregnated with pyrite, chalcopyrite, and a little molybdenite, and its contact with quartz monzonite is marked by a sericritic zone a few feet in width².

Lensing fissure veins with well banded quartz, argetiferous galena, and minor chalcopyrite that has been crushed. Gouge borders. Few pockets of wulfrenite. Oxidized near the surface to drusy quartz, psilomelane, lead and copper carbonates, and pockets of horn silver. Lead mineralization increased with depth. Deposit lies along a fault zone parallel to contact of Jurassic granite with Precambian metamorphics.⁵

Type of Operation and Production

The Benton mine is 2¼ miles south of Duquesne and about three-fourths of a mile north-northeast of post 113 of the international boundary. A party of four men was working on it in 1909. It comprise five claims lying in a north-south direction.

The development consists primarly of a 165-foot tunnel that trends N. 20° W. and is mainly in the quartz monzonite but toward the face passes through the granite porphyry, which at this point is 50 feet wide and is so highly and uniformly impregnated with pyrite and chalcopyrite that if forms a body of low-grade ore. The rock in the east side of the dike, in which the minerals more concentrated than elsewhere, is said to average 2% copper. The croppings of the dyke are iron stained and contain, in small fissures, little bodies or lenses of limonite, azurite, and malachite that are said to average about 14% copper and from $6 to $8 to the ton in gold².

Shaft operations. Mined by Mexicans prior to 1880 and sporadically to 1924. estimated and recorded production would be some 100 tons of ore average about 190 oz. Ag/T, 37% Pb, 0.1 oz. Au/T and minor Cu⁵.

References

1. Mineral Appraisal of Coronado National Forest, Part 12, Santa Rita Mountains Unit, MLA11-94 (1994). SR 591-609
   http://repository.azgs.az.gov/sites/default/files/dlio/files/nid1813/usbm_mla_011-94.pdf
2. Mining in the Santa Rita and Patagonia Mountains of Arizona, F. C. Schrader, U.S. Department of Interior, 1915. Republished 2014 by Kerby Jackson.
3. Mike Bertram,
4. USGS Mineral Resources Data System - using WGS84 (https://mrdata.usgs.gov/mrds/map-commodity.html#home)
5. Index of Mining Properties in Santa Cruz County by Stanton B. Keith, bulletin 1991, Arizona Geological Survey, 1975