Leonard Mine, Butte, Butte District (Summit Valley District), Silver Bow Co., Montana, USA
|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).
27 valid minerals.
Rock Types Recorded
Select Rock List TypeAlphabetical List Tree Diagram
Entries shown in red are rocks recorded for this region.
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 Macrostrat.org
66 - 145 Ma
66 - 145 Ma
|Biotite-hornblende granodioritic rocks along the Continental Divide, Anaconda Range, Sapphire Mountains, and Flint Creek Range|
Age: Cretaceous (66 - 145 Ma)
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.