The Crow Butte uranium deposit is a sandstone-type, roll-front uranium deposit, and is contained within the Chadron sandstone, at the base of the Oligocene Chadron Formation.

Petrographic data (e.g., U-bearing matrix at grain contacts) indicate that U mineralization occurred before lithification of the sandstone. Dissolution of abundant rhyolitic volcanic ash produced U- and Si-rich ground waters that were channeled through permeable sandstones at the base of the Chadron by relatively impermeable overlying and underlying beds. The precipitation of early authigenic pyrite created a reducing environment favorable for
precipitation and accumulation of U in the basal sandstone. The U has remained in a reduced state, as evidenced by the fact that the unoxidized minerals, coffinite and uraninite, comprise the bulk of the ore. At least some U and V remain bound to amorphous volcanic material and/or smectite rather than existing as discrete mineral phases.

The Chadron sandstone, which hosts the Crow Butte deposit, consists of coarse-grained, cross-bedded sandstone, with thin lenses of gravel-size conglomerate and interbedded clay layers. The sandstone is composed of 65% quartz, 25% feldspar and 10% rock fragments. The sediments also contain up to 30% air-fall ash in places.

Uranium is recovered at Crow Butte through the in situ process. There is no waste rock or tailings. Uranium is extracted from underground by pumping native groundwater mixed with small amounts of oxygen and bicarbonate (baking soda) into the ore zone. The uranium is freed from a sandstone formation and pumped to the surface for processing.

The uranium recovery process utilizes the following steps:
* Loading of uranium complexes onto an ion exchange resin;
* Reconstitution of the leach solution by addition of carbonate and an oxidizer;
* Elution of uranium complexes from the resin; and
* Drying and packaging of the uranium.

Recovery of uranium takes place in the ion exchange columns. The uranium bearing leach solution enters the column and as it passes through, the uranium complexes in solution are loaded onto the ion exchange (IX) resin in the column.

The now barren leach solution passes from the ion exchange columns to be reinjected into the formation. The solution is refortified with sodium and carbonate chemicals, as required, and pumped to the wellfield for reinjection into the formation.

Once the majority of the ion exchange sites on the resin in an ion exchange column are filled with uranium, the column is taken off stream. (In the current main process plant, t ........