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Alpha-Platus Mine (Golden Reward Group), Ruby Basin District, Lawrence Co., South Dakota, USA

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Latitude & Longitude (WGS84): 44° 20' 13'' North , 103° 48' 56'' West
Latitude & Longitude (decimal): 44.33694,-103.81555
Köppen climate type:Dfb : Warm-summer humid continental climate

Deposit:: -10650 P 78
Commodities (Major) - Silver, Gold
Deposit Type: Replacement
Development Status: Past Producer
Host Rock Unit: Deadwood Formation
Structure: Series Of Minor North - South Faults Complicates The Structure And The 91 M Tornado Fault Cuts Off The Mine To The West.

Mineral List

2 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

Eocene - Paleocene
33.9 - 66 Ma

ID: 3006792
Latitic Intrusive Rocks

Age: Paleogene (33.9 - 66 Ma)

Description: Dark-gray to greenish-gray laccoliths and sills of latite, latitic andesite, and quartz latite. Contains phenocrysts of andesine, oligoclase, biotite, hornblend, and sphene in a finely crystalline andesine-biotite-quartz groundmass.

Lithology: Major:{hypabyssal latite,hypabyssal andesite,hypabyssal quartz latite}

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]

Eocene - Paleocene
33.9 - 66 Ma

ID: 2473580
Phonolitic intrusive rocks

Age: Paleogene (33.9 - 66 Ma)

Description: Greenish gray, phaneritic. Typically, fresh exposures contrast with weathered intermediate-composition rocks. Forms laccolithic bodies, sills, and dikes.

Reference: Redden, J.A., E. DeWitt. Maps Showing Geology, Structure, and Geophysics of the Central Black Hills, South Dakota. U.S. Geological Survey Scientific Investigations Map 2777. [73]

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

This page contains all mineral locality references listed on This does not claim to be a complete list. If you know of more minerals from this site, please register so you can add to our database. This locality information is for reference purposes only. You should never attempt to visit any sites listed in without first ensuring that you have the permission of the land and/or mineral rights holders for access and that you are aware of all safety precautions necessary.
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