[en] The US Bureau of Mines is investigating the leachability of carbonaceous uranium ore samples submitted by the DOE under an Interagency Agreement. Studies on eight samples from the Great Divide Basin, Wyoming, are the basis of this report. The uranium content of the eight ore samples ranged from 0.003 to 0.03% U³O⁸ and contained 0.7 to 45% organic carbon. Experiments were performed to determine the feasibility of extracting uranium using acid leaching, roast-acid leaching and pressure leaching techniques. Acid leaching with 600 lb/ton H²SO⁴ plus 10 lb/ton NaClO³ for 18 h at 70₀C extracted 65 to 83% of the uranium. One sample responded best to a roast-leach treatment. When roasting for 4 h at 500₀C followed by acid leaching of the calcine using 600 lb/ton H²SO⁴, the uranium extraction was 82%. Two of the samples responded best to an oxidative pressure leach for 3 h at 200₀C under a total pressure of 260 psig; uranium extractions were 78 and 82%