Crooks Gap - Green Mountain uranium area

The Crooks Gap - Green Mountain uranium area is a uranium mine located in Fremont county, Wyoming.

About the MRDS Data:

All mine locations were obtained from the USGS Mineral Resources Data System. The locations and other information in this database have not been verified for accuracy. It should be assumed that all mines are on private property.

Mine Info

Name: Crooks Gap - Green Mountain uranium area  

State:  Wyoming

County:  Fremont


Commodity: Uranium

Lat, Long: 42.39, -107.82920

Map: View on Google Maps

Satelite View

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Satelite image of the Crooks Gap - Green Mountain uranium area

Crooks Gap - Green Mountain uranium area MRDS details

Site Name

Primary: Crooks Gap - Green Mountain uranium area
Secondary: Sheep Mountain No. 1
Secondary: Sheep Mountain No. 2
Secondary: Pay Dirt Pit
Secondary: Reserve Mine
Secondary: Golden Goose I
Secondary: Golden Goose II
Secondary: Congo, Shinkolobwe, Section 16 Mine
Secondary: Snowball Mine (includes Sno-ball claims)
Secondary: Sundog Mine
Secondary: Helen May Mine
Secondary: Hazel Claim, Beatrice Claims
Secondary: Utah Mine (Utah International, Inc.)
Secondary: Seismic Mine
Secondary: Jeffrey Ctiy (ambiguous)
Secondary: Beatrice Group
Secondary: Fred's Folly
Secondary: Trey and Cindy claims
Secondary: Crooks Gap - Green Mountain Uranium District


Primary: Uranium


State: Wyoming
County: Fremont
District: Crooks Gap - Green Mountain uranium area

Land Status

Not available


Not available


Not available


Not available


Year: 2010
Mined: 4389811.000 mt
Material type: 4,838,938 short tons ore from 7 mines.


Record Type: District
Operation Category: Past Producer
Operation Type: Surface-Underground
Years of Production:
Significant: Y


Not available

Mineral Deposit Model

Model Name: Sandstone U


Not available


Type: L
Structure: synclinal troughs


Not available


Not available

Analytical Data

Analytical Data: Grade of ore mined is reported to be in the range: 0.18 to 0.23% U3O8.


Ore: Autunite
Ore: Coffinite
Ore: Uranophane
Ore: Uraninite
Gangue: Selenium
Gangue: Pyrite
Gangue: Calcite


Comment (Location): Fred's Folly Claim is shown on p. 67 of 115, DMEA-3462 in extreme NE4 of Sec. 21. This would be where the Reserve Mine is.

Comment (Production): According to the values reported on MS-94 (Gregory and others, 2010), the 7 productive mines in the district produced a total of 4,838,438 short tons of ore (not uranium). There is no mention of the ore grade, therefore total contained uranium can not be estimated. The productive mines are Hazel and Beatrice (23 tons), Crooks Gap Mines (3,300,000 tons), Green Mountain (523,438 tons), Sundog (139 tons), Snowball and Pay Dirt (267,446 tons), Heald (6,641 tons), and Big Eagle (741,251 tons).

Comment (General): Mill or processing facility is north of Jeffrey City.

Comment (Ownership): Trey and Cindy claims were held by Mile High Minerals, Denver, CO, as of 1956. See DMEA Docket No. 3992. Last few pages of Docket contains useful and accurate location maps, especially relative to the Sun, Sundog, and Snowball Claims.

Comment (General): From TEI-440, p. 180: " Yellow uranium minerals occur in sec. 32, T28N, R92W, in arkosic conglomeratic sandstone in the lower Eocene rocks on the east side of Crooks Gap. The locality has been examined by geologists of the AEC. Minerals were observed in places thorugh a section of about 75 feet of rocks, but are concentrated adjacent to carbonaceous shale partings, carbonized wood fragments, and in highly ferruginous zones. The mineral was indentified as phosphuranylite [formula omitted here], and a selected sample contains 0.17 dU. The uranium-bearing zone is about 200 feet above the base of a sequence of brown and gray coarse clastic rocks, chiefly arkosic sandstones containing lenses of giant granite boulders, variegated claystones, and carbonacous shale, the total thickness of which is more than 1,000 feet. A sample of water from a spring, likewise in sec. 32, T25N, R92W, contained 250 ppb of U. The uranium appears to have been deposited in many places where there are concentrations of carbonized wood fragments, carbonaceous shale partings, or very ferruginous sandstones."


Reference (Location): Geological Survey of Wyoming, 1970, Mines and Minerals Map of Wyoming: Geological Survey of Wyoming, scale 1:500,000.

Reference (Deposit): MINOBRAS, 1976, Uranium Guidebook for Wyoming, 63 p. and appendix.
Pages: p. 29-31.

Reference (Deposit): DMEA Docket No. 3462, 115 p.,

Reference (Deposit): Love, J.D., 1954, Wyoming, in Geological investigations of radioactive deposits, semiannual progress report, December 1, 1953 to may 31, 1954: U.S. Atomic Energy Commission TEI-440, 245 p.
Pages: p. 180.

Reference (Deposit): Stephens, J.G., 1964, Geology and uranium depoists at Crooks Gap, Fremont County, Wyoming: U.S. Geological Survey Bulletin 1147-F, 82 p, plate 1, scale 1:48,000.
Pages: pl. 1 (1:48,000), p. 43--49.

Reference (Production): MINING MAGAZINE, 1989, p. 45.
Pages: p. 45.

Reference (Deposit): Gregory, R.W., Jones, R.W., and Cottingham, K.D., 2010, Uranium Map of Wyoming: Wyoming State Geological Survey Map Series 94, scale 1:500,000.

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