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When uranium ore is mined and processed in the conventional crushing plant there is little urgency to know what mineral contains the uranium and how that mineral is distributed within the ore. However, solution mining techniques depend for their success on bringing the dissolving solutions into contact with the uranium-bearing mineral and dissolving it. With that requirement in mind, a study was undertaken to help understand the character and location of the uranium-bearing mineral in the Oakville Sandstone of south Texas where solution mining is being carried out.

Thin-section and electron-microprobe analyses were conducted on a sample of high concentration ore to confirm that uranium was located in the space between framework sand grains. Moreover, uranium was not uniformly distributed throughout the silt and clay intergranular matrix material. The disaggregated and fractionated sandstone showed the highest concentration of uranium to be in the silt-size fraction. Further separation of the ore was carried out by heavy liquids and magnetic fractionations. The uranium-bearing mineral was concentrated along with dense and magnetic minerals. Openwork intergrowths of pyrite crystals made up most of this fraction. In spite of having concentrated uranium in excess of 43,000 ppm U₃O₈, it was still not possible to identify any ura ium-bearing mineral by X-ray diffraction. This suggests that uranium may be held in the sandstone as an amorphous oxide.

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