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St. Louis Mine (Morning Star Mine; Isabel), St. Louis Gulch, Hughes Gulch, Greaterville placer deposits, Greaterville, Greaterville District, Santa Rita Mts, Pima Co., Arizona, USA

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Latitude & Longitude (WGS84): 31° 45' 32'' North , 110° 45' 48'' West
Latitude & Longitude (decimal): 31.7588888889, -110.763333333
Other regions containing this locality:Sonoran Desert, North America

‡Ref.: Schrader, F.C. & J.M. Hill (1915), Mineral deposits of the Santa Rita and Patagonia Mountains, Arizona, USGS Bull. 582: 153, 155-156.

Wilson, E.D. (1927), Arizona gold placers, 2nd. Edition (revised), University of Arizona Bull. 124: 36, 40.

Drewes, Harald (1970) Structural control of geochemical anomalies in the Greaterville mining district, southeast of Tucson: U.S. Geological Survey Bulletin 1312-A, p. A1-A49, 1 sheet, scale 1:24,000.

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.

Stewart, J.C. (1971) Geology of the Morningstar Mine area, Greaterville Mining district, Pima County, Arizona: Tucson, University of Arizona, M.S. thesis, 79 p.

Keith, Stanton B. (1974), AZ Bur. of Geol. & Min. Technology, Geol. Survey Br. Bull. 189, Index of Mining Properties in Pima County, AZ: 121 (Table 4).

USGS Sahuarita Quadrangle topo map.

Arizona Bureau of Mines file data.

MRDS database Dep. ID file #10039494, MRDS ID #M050166; and, Dep. ID #10258933, MAS ID #0040190417.

A former small underground Pb-Zn-Ag-Cu-Au-Mo mine located in the NE ¼ sec. 25, T.19S., R.15E., about ¾ mile west of Greaterville, at the SE base of Granite Mountain, on the east side of St. Louis Gulch, near its junction with Hughes Gulch, on the eastern foot of the Santa Rita Mountains, at an elevation of 5,495 feet. Located about 37 miles SE of Tucson. A group of approximately 10 contiguous claims. Located in 1874. Owned/operated at times, or in part, by the Liberty Silver Mines Co.; Otey & Forney; Martinez; the St. Louis Mines, Inc., and Anaconda (1969- ?). Owned by Mr. Austin Mitchell og Elgin, IL (1969).

Mineralization is a compound vein or lode about 8 feet wide, composed of quartz veins and numerous small rhyolite dikes and contained in a NE-SW shear zone about 800 feet wide and 3,000 feet long, in altered shales, hornfels, and silicified dolomitic limestone, localized along the crest and upper flanks of SW limb of a NW-trending anticline. This zone lies at the SE base of Granite Mountain, and the intrusion of the granite porphyry forming the mountain deformed and metamorphosed the Cretaceous sediments. The veins in the lode are limited and form a stockwork. The lode dips 45º SE, away from the mountain, about parallel with the inclosing rocks, and its dip seems to flatten in depth on receding from the mountain. Almost throughout the extent of the lode occur numerous mineral-bearing quartz stringers. Ore is spotty, partially oxidized, aergentiferous galena with other sulfides. High-grade pockets of gold in the iron oxide capping. The host rock unit is the Apache Canyon Formation. Age of mineralization believed to be that of quartz latite intrusive of Drewes - 1971.

Gols is common in the upper part of the mine, yet very erratically. Minerals occur as fine to coarse disseminated grains and as aggregates of mixed minerals in bands and clumps. Lead is primarily in the vein and values increase with depth until the 140 foot level, where it drops appreciably. Zinc values correspond with lead. Copper values decline with depth and away from the vein. High Ag values correlate with high values of Pb and Zn, concentrated about the 90 foot level. Mo is evenly distributed throughout the vein and the wallrock. Gold appears to have higher values near small flexures within the veinlets. Oxidized down to the 20 foot level. The ore body is 6.1 meters wide and 0.61 meters thick, striking N55E and dipping 33SE.

Local structures include tilting and broad open folds in the south and extensive faulting in the north, homoclinal. Attitude of veins is generally conformable to bedding at N50-60E, and with a 28-38SE dip; and, a NE-trending shear zone.

Workings include tunnel and a 75 foot shaft a 241 foot inclined shaft, drifts, a raise, small stopes. The workings are 57.91 meters deep and 213.36 meters long. A sporadic production occurred from 1875 to 1946 of some 300 or more tons of ore averaging about 6% Pb, 7% Zn, 11 oz. Ag/T, 0.5 oz. Au/T and 1% Cu. Sporadic production from 1875 to 1966.

This is the only old mine in the district to be actively maintained and has been recently further developed. Judged in 1969 to be uneconomical to mine due to small size, too low grade, and erratic distribution of ore minerals. Extensions of the vein system in depth and laterally are not encouraging. Potential for a copper - molybdenum-bearing porphyry type deposit should not be discounted though.

Mineral List

10 valid minerals.

Regional Geology

This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.

Click on geological units on the map for more information. Click here to view full-screen map on

Campanian - Oxfordian
72.1 - 163.5 Ma
Cretaceous to Late Jurassic sedimentary rocks with minor volcanic rocks

Age: Mesozoic (72.1 - 163.5 Ma)

Stratigraphic Name: Temporal Formation; Bathtub Formation; Sand Wells Formation; Fort Crittenden Formation; McCoy Mountains Formation

Description: Sandstone and conglomerate, rarely forms prominent outcrops; massive conglomerate is typical near base of unit and locally in upper part. These deposits are nonmarine except in southeastern Arizona, where prominent gray marine limestone (Mural Limestone) forms the middle of the Bisbee Group. Sandstones are typically medium-bedded, drab brown, lithic-feldspathic arenites. Includes Bisbee Group (largely Early Cretaceous) and related rocks, Temporal, Bathtub, and Sand Wells formations, rocks of Gu Achi, McCoy Mountains Formation, and Upper Cretaceous Fort Crittenden Formation and equivalent rocks. (80-160 Ma)

Lithology: Major:{arenite,conglomerate}, Minor:{limestone}

Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052. [133]

Data and map coding provided by, used under Creative Commons Attribution 4.0 License

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