Evidence resulting from geologic mapping in the southern Black Hills indicates that the areas marginal to some of the larger carbonate-cemented sandstones constitute favorable geochemical environments for the localization of uranium deposits. To determine whether these favorable environments are predictable a limited experimental core-drilling program was carried out. An extensive deposit was discovered in an area marginal to a sandstone well-cemented with calcium carbonate. The deposit has not yet been developed, but from the available data it appears that there is a significant quantity of mineralized rock present containing as much as 3.0 percent eU3O8.