Mining Intelligence and News
United States

Lost Creek Mine

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Mine TypeIn-Situ
  • Uranium
Mining Method
  • Solution mining
Production Start... Lock
Mine Life... Lock
SnapshotCommercial production at Lost Creek restarted in May 2023 with HH2-4.

The first two mine units at Lost Creek (MU1 and MU2) have all appropriate permits necessary for a return to commercial level operations, including production resulting from ongoing MU2 construction and development.

Ur-Energy awaits only the approval by the Wyoming Department of Environmental Quality, Land Quality Division (“LQD”) of the amendment to the Lost Creek permit to mine adding HJ and KM horizons at LC East and HJ mine units at Lost Creek. It is anticipated the LQD review will be complete in 2023.


Ur-Energy Inc. 100 % Indirect
Lost Creek ISR, LLC (operator) 100 % Direct
Ur-Energy USA has three wholly-owned subsidiaries: NFU Wyoming, LLC, Lost Creek ISR, LLC, and Pathfinder Mines Corporation.

Lost Creek ISR, LLC, is a limited liability company formed under the laws of the State of Wyoming to hold and operate the Lost Creek Project and certain other Lost Creek properties and assets.



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Deposit type

  • Sandstone hosted


Mineralization of the Lost Creek Property
Mineralization at the Lost Creek Project and Adjoining Projects occurs as roll front type uranium deposits.

Mineralization occurs in sand horizons within the Eocene-age Battle Spring Formation. The most significant mineral resources in the Property occur within two major stratigraphic horizons, the HJ and the KM Horizons. The HJ Horizon contains most of the currently defined mineral resources and hosts the current production zones. As discussed earlier, the HJ Horizon is subdivided into four stratigraphic sub-horizons that are also used for resource reporting. The highest abundance of uranium mineralization occurs in the MHJ1 and MHJ2 sub-horizons. Each sub-horizon, in turn, may consist of multiple mineralized roll fronts. The HJ Horizon, as a whole, contains up to 11 individual roll fronts within a stratigraphic interval of approximately 130 ft.

The KM Horizon underlies the HJ Horizon and contains additional significant mineralization that will be targeted for future production later in the Lost Creek mine plan. Mine approvals for the KM Horizon have and will be addressed by amendments to the mine license and permits. To date, a total of nine individual roll fronts have been identified in the KM Horizon within a stratigraphic interval of approximately 100 ft.

Mineral resources that are currently targeted for mining in the Property occur within two major trends. In the Lost Creek Project, resources are focused in the east-west oriented MMT that is approximately three miles long and 500 to 2,000 ft. wide. Mineralization targeted for mining has also been identified within the underlying KM Horizon and the overlying FG Horizon.

A second mineralized trend of significance, the EMT, was identified by historical drilling within the LC East Project. Although geologically similar, it appears to be a separate and independent trend from the MMT and is believed to be the product of a different mineralization system. The EMT assumes a generalized northeast-southwest orientation extending for approximately six and one-half miles with a width of 500 to 1,500 ft. As in the MMT, the known mineralization occurs mainly in the HJ and KM Horizons. Significant occurrences have also been identified in the FG Horizon.

Geological evaluations of historical and URE drill data have resulted in the recognition of numerous additional uranium occurrences within the Property. Historical exploration drilling by previous operators was conducted within all project areas. In addition, URE has conducted exploration drilling in the LC North, LC South, and EN Projects plus limited exploration drilling in LC East.

Mineralization has also been recognized throughout the Property in horizons deeper than the KM, in what are referred to as the Deep Horizons (L, M and N). Recent and historical drill hole data confirm multiple roll fronts with locally identified Inferred resources in these horizons. URE anticipates conducting future exploration drilling to further define the resource potential of these stratigraphic horizons.

Mineralogy of the zones of interest has been studied in thin section and by x-ray diffraction analysis. Mineralogical analyses were conducted in 1979 by Russell Honea (Honea, 1979a and b), and in 2007 by Hazen Research, Inc. (Hazen Research) (Hazen, 2007) on samples derived from core. Results indicate that the uranium occurs primarily as the mineral coffinite (uranium silicate) in the form of micron- to submicron-size inclusions disseminated in and on interstitial clay, possibly absorbed by cation exchange; also intimately interspersed through some of the pyrite and as partial coatings on quartz and biotite. Minor amounts of uraninite (uranium oxide) and brannerite (uranium-titanium oxide) have also been identified. Clay rich fractions are predominantly smectite (montmorillonite), with minor kaolinite.

Uranium mineralization identified throughout the Property occurs as roll front type deposits, typical in most respects of those observed in other Tertiary Basins in Wyoming. t. The formation of roll front deposits is largely a groundwater process that occurs under favorable geochemical conditions. The most favorable host rocks for roll fronts are permeable sandstones within large aquifer systems. Interbedded mudstone, claystone and siltstone are often present and aid in the formation process by focusing groundwater flow.

The geometry of mineralization is dominated by the classic roll front “C” shape or crescent configuration at the alteration interface. The highest-grade portion of the front occurs in a zone termed the “Nose” within reduced ground just ahead of the alteration front. Ahead of the Nose, at the leading edge of the solution front, uranium quantity gradually diminishes to barren within the “Seepage” zone. Trailing behind the “Nose”, in oxidized (altered) ground, are weak remnants of mineralization referred to as “Tails” which have resisted re-mobilization to the Nose due to association with shale or other lithology of lower permeability. Tails are generally not amenable to in situ recovery because the uranium is typically within strongly reduced or impermeable strata, therefore making it difficult to leach.

The source of the uranium within the Property is speculative. Boberg (2010) suggests that the source within this portion of the Wyoming Uranium Province is a combination of leaching of uraniferous Oligocene volcaniclastics that once covered the basins and the weathering and leaching of uraniferous Archean granite of the Granite Mountains (north of the GDB) which also represent the provenance of the arkosic sands comprising the Battle Spring Formation.

Oxygenated surface water passing through the overlying thick sequences of volcaniclastic material may have leached metals, including uranium. These metal-enriched fluids may have also leached additional uranium from the arkosic sands that compose the aquifers. The enriched, oxidizing fluids subsequently entered the regional groundwater systems within the basin and migrated down-dip through the aquifers as large oxidizing geochemical cells referred to as solution fronts.

Uranium precipitated in the form of roll front deposits at the leading edge of the geochemical cells where the transporting water encountered reducing geochemical environments within the host sands. Uranium quantity was enhanced where groundwater flux was focused horizontally by paleochannels or vertically by aquitards. Continuity of these conditions produced a significant accumulation of uranium at the reduction-oxidation (redox front) interface. In addition, the continued supply of oxygen to the interface leads to degradation of the reduced strata and resulted in migration down gradient of the redox interface, thus remobilizing the associated uranium with it. In this manner the uranium deposit slowly migrated down-dip over geologic time.

The reducing environment in the host sand is generally induced by carbonaceous material within the formation or leaked reductant gases originating from deep hydrocarbon sources. Pyrite is inherently associated with both and is a significant indicator of a reducing environment. Reduced sands are typically some shade of gray and represent the regional framework prior to mineralization. The reducing environment is subsequently altered by the passage of the oxidizing solution front. The total length of a mineralization trend may extend for several miles. Commonly, a deposit or mineralized trend will consist of a composite of multiple, vertically stacked roll fronts.

Typical width of an individual roll front is generally 25 to 100 ft. However, in the case of multiple stacked fronts, the composite width may be several hundred feet across. Typical thickness of an individual roll front is roughly 5 to 25 ft., and the composite thickness of multiple, vertically stacked fronts may occupy as much as 200 ft.



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Mining Methods


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Crushers and Mills

Milling equipment has not been reported.



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Due to persistent low uranium prices, Ur-Energy has limited its production operations since the third quarter of 2020. During 2021, Ur-Energy captured 251 pounds of U3O8 and during 2022, Ur-Energy captured 325 pounds of U3O8 at the Lost Creek plant. All of Ur-Energy sales made in 2020 were of purchased inventory. Ur-Energy made no sales of U3O8 in either 2021 or 2022.
All production numbers are expressed as U3O8.

Operational metrics

Annual production capacity  ....  Subscribe  ....  Subscribe2 M lbs of uranium U3O82 M lbs of uranium U3O82 M lbs of uranium U3O82 M lbs of uranium U3O8

Production Costs

Cash costs U3O8 USD  ....  Subscribe 18 / lb   23.9 / lb   29.5 / lb  


Sustaining costs M USD 0.3   0.3   0.5  
Revenue M USD  ....  Subscribe 32.3   23.5   38.4  
Operating Income M USD  ....  Subscribe 8.3   1.3  
Gross profit M USD  ....  Subscribe 2   11.3   14  
After-tax Income M USD  ....  Subscribe 8.4   4.5   0.08  

Heavy Mobile Equipment


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Mine Management

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Aerial view:


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