San Miguel bench includes about 4 square miles in the southern part of T. 48 N., R. 17 W., New Mexico principal meridian, Montrose County, Colorado.
Production of carnotite ore from the area has been about 15,000 short tons having an estimated average grade of 0.31 percent U3O8 and 1.6 percent V2O5.
Nearly all of the carnotite deposits occur in a single continuous sandstone bed near the top of the Salt Wash member of the Jurassic Morrison formation. These deposits consist chiefly of sandstone impregnated with uranium- and vanadium-bearing minerals. They are irregular tabular-shaped masses ranging in size from a few short tons to 30,000 short tons or more of minable carnotite ore.
During the period November 27, 1951, to April 17, 1953, the U.S. Geological Survey drilled 309 holes totaling 92,194 feet on the San Miguel bench.
Reserves total about 43,000 short tons of material 1 foot or more thick and contain 0.10 percent or More U3O8 or 1.0 percent or more V2O5. Of these reserves 3,300 short tons occur in private land. These reserves are in ten deposits found by Geological Survey drilling. Potential reserves (reserves based on geologic evidence only) are predicted to total about 15,000 short tons, averaging 0.30 percent U3O8 and 1.6 percent V2O5.
No additional drilling in the San Miguel bench is planned by the Geological Survey. Some drilling by private enterprise is recommended.