From introduction: To improve understanding of uranium mineralization of the Todilto Limestone of Late Jurassic age in the Grants district, New Mexico, the mines active in 1957 were reviewed to determine the major types of deposits. A representative example of each type was selected and mapped in great detail to establish a prototype. It was hoped that the analysis of prototypes might shed considerable light on the mineralization process and aid evaluation of other deposits by offering a standard of comparison.