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Leonard Mine, Butte, Butte District (Summit Valley District), Silver Bow Co., Montana, USA

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Latitude & Longitude (WGS84): 46° 1' 14'' North , 112° 30' 18'' West
Latitude & Longitude (decimal): 46.02073,-112.50506
Köppen climate type:Dfb : Warm-summer humid continental climate

A former Cu-Ag-W-Pb-Zn mine located in secs. 7 & 89. T3N, R7W, MPM, E of the Berkeley pit, on private land. Discovered in 1886. The first production occurred in 1887. Owned and operated by the Anaconda Co., Butte, Montana 59701. MRDS database accuracy for this location is not stated.

Mineralisation is a polymetallic deposit hosted in quartz monzonite and granite. The ore body strikes N70E and dips steeply S. Ore is principally from horsetail ore bodies of the eastern portion of the main district & NW-trending main stage veins. The largest masses of quartz porphyry in the district are found near the Leonard & East Colusa shafts - these bodies are in or near the horsetail ore zone of the central district. Copper mineralisation occurs in horsetail ore bodies and NW-trending main stage veins. The ore body in places consisted of a mass of crushed granite. The ground between the veins was netted, lesser streaks were abundant and in many places, the granite was cobwebbed with ore. Local alteration includes main stage alteration. Associated rocks include Late Cretaceous quartz monzonite (Boulder batholith). Local rocks include alluvium.

Geologic structures include the regional Boulder batholith and the local Rarus fault.

Mining has been exclusively on selective veins of both ages W of the middle fault, on horsetail bodies and selective veins between the middle fault and No. 20 fault. Very little exploration and development work have been carried out E of the No. 20 fault.

Note: Rhodochrosite specimens labelled as from the Leonard Mine are most likely not from this mine. Rhodochrosite should not have occurred at this mine. (Ref: Min. Rec. 33: 1).

Mineral List

27 valid minerals.

Rock Types Recorded

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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.

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66 - 145 Ma

ID: 2984479
Granitic rock

Age: Cretaceous (66 - 145 Ma)

Lithology: Major:{granitic}

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]

66 - 145 Ma

ID: 2108663
Biotite-hornblende granodioritic rocks along the Continental Divide, Anaconda Range, Sapphire Mountains, and Flint Creek Range

Age: Cretaceous (66 - 145 Ma)

Lithology: Major:: {biotite-hornblende granodiorite, biotite-hornblende monzogranite, tonalite}

Reference: Zientek, M.L., P.D. Derkey, R.J. Miller, J.D. Causet et al. Spatial Databases for the Geology of the Northern Rocky Mountains - Idaho, Montana, and Washington. U.S. Geological Survey Open-File Report 2005-1235 Version 1.0. [25]

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.


Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Weed, W. (1912) Geology and Ore Deposits of the Butte District, Montana.
Sales, R.H. (1914) Ore Deposits at Butte, Montana, The Mineralogy of The Butte District, Montana.
Guilbert and Zeihen (1964).
Miller, R.N. (editor) (1973) Guidebook for the Butte Field Meeting, presented by the Society of Economic Geologists.
Roberts et al. (1974) Encyclopedia of Minerals. Van Nostrand Reinhold Co.
Montana Bureau of Mines & Geology (1975) Bulletin 95: 25.
Rocks & Minerals (1986) 61: 12.
Rocks & Minerals (1987) 62: 323.
Mineralogical Record (2002) 33: 1.
USGS (2005) Mineral Resources Data System (MRDS): U.S. Geological Survey, Reston, Virginia, loc. file ID #10070469 & 10172707.
U.S. Bureau of Mines, Minerals Availability System (MAS) file ID #0300930005.
Montana Bureau of Mines & Geology, Bulletin 109: 19.
USGS Professional Paper 74: 210-15, Pl. X.

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