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Smoky Butte (Smoky Butte Lamproite), Garfield Co., Montana, USA

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Latitude & Longitude (WGS84): 48° 18' North , 115° 24' West
Latitude & Longitude (decimal): 48.30000,-115.40000
Köppen climate type:Dfb : Warm-summer humid continental climate

Note: massive samples consisting of small crystalline grains of chromite have been erroneously attributed to this locality.

Mineral List

19 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

0.0117 - 2.588 Ma

ID: 2092071
Glacial deposits

Age: Pleistocene (0.0117 - 2.588 Ma)

Description: glacial till, glacial outwash, fluvioglacial deposits; dune sands, lacustrine deposits

Lithology: Sand, gravel

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]

1000 - 1600 Ma

ID: 2939441
Piegan Group: Helena and Wallace Formations

Age: Mesoproterozoic (1000 - 1600 Ma)

Stratigraphic Name: Helena Formation; Wallace Formation

Description: Helena Formation (Yh): Northwestern Montana: (formerly “lower Wallace”): cycles of basal white quartzite or intraclast beds overlain by couplets of green siltite and argillite, capped by dolomite beds. Calcite pods and ribbons (molar tooth structure) common. West-central Montana: gray to dark gray limestone and dolomitic limestone with siltite partings. Thickness as much as 2,000 m (6,562). Wallace Formation: Tan-weathering, dolomitic quartzite and siltite, and black argillite with calcite ribbons (molar tooth structure) in graded pinch-and-swell couples and couplets. Thickness as much as 2,500 m (8,202 ft).

Lithology: Major:{quartzite,metasiltstone,argillite}, Minor:{limestone,dolostone}

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]

1000 - 1600 Ma

ID: 3186914
Mesoproterozoic sedimentary and volcanic rocks

Age: Mesoproterozoic (1000 - 1600 Ma)

Stratigraphic Name: Purcell Group

Comments: Omineca Belt

Lithology: Mafic-intermediate volcanic rocks; limestone,shale,argillite,quartzite,dolomite,siltstone; turbidite

Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. [154]

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)
Matson, Robert Ernest (1960) Petrography and petrology of Smoky Butte intrusives, Garfield County, Montana. Thesis University of Montana.
Velde, Danielle (1975) Armalcolite-Ti-phlogopite-diopside-analcite- bearing lamproites from Smoky Butte, Garfield County, Montana. American Mineralogist: 60: 566-573.
Wagner, Christiane and Velde, Danielle (1986) Davanite, K2TiSi6O15, in the Smoky Butte (Montana) lamproites, American Mineralogist: 71(11-12): 1473-1475.

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