The Dolores bench is about 2 miles northwest of Uravan, Montrose County, Colo. From 1913 to November 1952 about 95,000 short tons of ore averaging 0.40 percent U3O8 and 2.0 percent V2O5 was mined from the Dolores bench. The production represents three periods of activity--1913-18, 1938-43, and 1948-52.
The ore deposits are in broad sandstone lenses near the top of the Salt Wash member of the Jurassic Morrison formation. The deposits are mainly impregnations of sandstone by carnotite and vanadiferous clay minerals. The deposits are irregular tabular layers which occasionally include pod-like masses called “rolls”. The rolls as well as the mineralized areas enclosing them have a poorly defined northeast trend.
Between December 4, 1951, and August 1, 1952, the U.S. Geological Survey diamond-drilled 183 holes totaling 53,654 feet.
The indicated and inferred reserves of carnotite-bearing material, and the pounds of contained U3O8 and V2O5 area summarized in table 1. At the highest thickness and grade cutoffs (1 foot thick and 0.10 percent U3O8 or 1.0 percent V2O5), indicated and inferred ore reserves total 90,000 short tons, averaging 0.33 percent U3O8 and 2.11 percent V2O5. These reserves include only those discovered by U.S. Geological Survey drilling. Potential reserves, whose existence is based on geologic evidence alone, are estimated to be about 10,000 short tons, averaging about 0.30 percent U3O8 and 2.00 percent V2O5.
No additional exploration of the Dolores bench is planned by the Geological Survey. Diamond drilling by claim owners is recommended in several parts of the area.