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Midnite Mine (Midnight Mine; Boyd lease), Wellpinit, Stevens Co., Washington, USA

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Latitude & Longitude (WGS84): 47° 56' 26'' North , 118° 5' 31'' West
Latitude & Longitude (decimal): 47.94056,-118.09222
GeoHash:G#: c2s08xrcg
Other regions containing this locality:Rocky Mountains, North America
Locality type:Mine
Köppen climate type:Csb : Warm-summer Mediterranean climate

An U occurrence/mine located in secs. 1 & 12, T28, R37E, on the flank of Spokane Mountain, 10 miles NW of Wellpinit.

The geology is tabular uranium deposits at the contact of monzogranite of the Cretaceuos Midnite Mine pluton with metapelites and metacarbonates of the Proterozoic Togo Formation.

It produced ore from 1954 to 1982 leaving water filled pits and waste piles.

Leaching of the uranium and heavy metals into the water supply placed the Midnite Mine on list of Superfund cleanup sites for environmental hazards. Cleanup still has not been completed. Collecting is not allowed.

Mineral List

32 valid minerals.


Mineralization age: Eocene : 51 ± 0.5 Ma

Important note: This table is based only on rock and mineral ages recorded below and is not necessarily a complete representation of the geochronology, but does give an indication of possible mineralization events relevant to this locality. As more age information is added this table may expand in the future. A break in the table simply indicates a lack of data entered here, not necessarily a break in the geologic sequence. Grey background entries are from different, related, localities.

Geologic TimeRocks, Minerals and Events
ⓘ Uraninite51 ± 0.5 Ma

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 Macrostrat.org

66 - 145 Ma

ID: 3193051
Mesozoic intrusive rocks

Age: Cretaceous (66 - 145 Ma)

Lithology: Intrusive igneous rocks

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]

541 - 2500 Ma

ID: 2945791
Precambrian rocks, undivided

Age: Proterozoic (541 - 2500 Ma)

Stratigraphic Name: Striped Peak Formation; Wallace Formation; Ravalli Group; Prichard Formation; Edna Dolomite; McHale Shale; Togo Formation; Buffalo Hump Formation; No Name Argillite; Skookum Formation; Bead Lake Formation; Huckleberry Formation; Monk Formation; Three Sisters Formation; Maitlen Phyllite

Description: Predominantly phyllite with some schist, limestone, dolomite, quartzite, and volcanic rocks; northeastern Pend Oreille County. Mainly quartzite sandstone in upper part, dark-gray argillite with sandstone and limestone in middle part, and sandstone with argillite in lower part; southeastern Pend Oreille County. Banded slate with quartzite and dolomite; southwestern Stevens County. Quartzite, siliceous argillite, and argilliceous quartzite grading into argillite and quartz-mica schists form south ot north; southeastern Stevens County. Quartzite, argillite, quartz-feldspar gneiss, and other metamorphic rocks in northeastern Whitman and southeastern Spokane Counties are partly if not all extenstions of the Belt strata.

Comments: Belt Supergroup (Striped Peak Formation, Wallace Formation, Ravalli Group, Prichard Formation); Deer Trail Group (Edna Dolomite, McHale Shale, Togo Formation, Buffalo Hump Fomation); Priest River Group; No Name Argillite; Skookum Formation; Bead Lake Formation; Windermere Supergroup (in small part: mostly mapped as units WAPCc (Huckleberry Formation), WAPCv (Huckleberry Foramation), and WAPCph (Monk Formation and Three Sisters Formation)); Maitlen Phyllite (in part)

Lithology: Major:{argillite,siltstone}, Minor:{quartzite,dolostone,phyllite}, Incidental:{limestone, gneiss, schist, sandstone}

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: 1396332
Togo Formation, Deer Trail Group

Age: Mesoproterozoic (1000 - 1600 Ma)

Stratigraphic Name: Togo Formation

Lithology: Argillite

Reference: Washington State Department of Natural Resources, Division of Geology and Earth Resources. Washington Interactive Geologic Map: 1:100,000 scale. Washington Division of Geology and Earth Resources. [19]

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

This page contains all mineral locality references listed on mindat.org. 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 mindat.org 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)
Huntting, M. (1956) Inventory of Washington Minerals, Part II, Metallic Minerals, Vol. 1.
Barrington, J., & Kerr, P. F. (1961) Uranium mineralization at the Midnite mine, Spokane, Washington. Economic Geology: 56(2): 241-258.
Becraft, George E. and Paul L. Weis (1963) Geology and mineral deposits of the Turtle Lake quadrangle, Washington. USGS Bulletin 1131.
von Backstrom, J. W. (1974). Other uranium deposit. In IAEA Symposium on the formation of uranium ore deposits. Athens, Greece: 605-624.
Cannon, B. (1975) Minerals of Washington: 53, 76, 81.
Nash, J. T., & Lehrman, N. J. (1975) Geology of the Midnite uranium mine, Stevens County, Washington; a preliminary report. USGS Open File Report (OFR) 75-402.
Lasmanis, R. et al (1990) Metal Mines of Washington-Preliminary Report.

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