In the White Signal district, secondary uranium phosphates occur in the oxidized portions of gold-pyrite-quartz veins and in adjacent fractures. Nature of primary mineralization is unknown. Concentrations are believed to result from oxidation of veins and fixation of uranium by phosphate from neighboring diabase dikes. In the Bullard Peak district, uraninite is associated with nickel and cobalt arsenides and sulfarsenides toward the margins of veins that have native silver in their central portions. The uraninite may represent the last phase of silver and base-metal mineralization or be related fluorspar and gold mineralization of nearby areas. Its source is probably a nearby Laramide monzonitic intrusion.

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