Abstract

Uranium mining has been significant in Wyoming sandstones since the late 1950's. The outlook is for continued important production for many years. The principal known uranium deposits occur as rolls in sands of early Eocene, Paleocene, and Early Cretaceous ages.

The chief mining method to-date has been the open pit, although underground mining is likely to become increasingly important with the discovery of progressively deeper deposits. Open-pit mining has definite advantages over underground mining, chief of which are lower costs and higher realization of ore reserves. However, stripping has a practicable depth limitation, presently about 400 feet, below which underground mining is usually less costly. The increase during the last decade of geological knowledge regarding the occurrence of roll-ore bodies in Wyoming has resulted in improvements in mining techniques, and has been especially helpful in exploring for, discovering, and eventually mining small ore rolls that might once have been left behind by underground mining operations.

Ranges and averages of open-pit and underground mining costs are presented in two tables. Various factors that effect increases in these costs from the low to the high range are discussed.

Minor uranium production has been obtained from in situ leaching in the Shirley Basin district of Wyoming, but the process has not yet become competetive with conventional methods as an important mining method.