The silver-bearing copper-lead-zinc ores occur in tabular veins occupying steeply dipping oblique fractures in altered Permian volcanic rocks, silicated Jurassic limestones of the Potosi formation, and quartz monzonite stocks, in vertical pipes mainly along intrusive contacts, and in gently plunging mantos. Many of the pipes and mantos, which are most abundant in the western part of the district, grade upward into vein structurs. Controls over localization of ore shoots in the veins include dilation of the wall rock, mineral zoning with respect to centers of mineralization, and depth. The pipes and mantos were localized chiefly by fracture intersections and intrusive and alteration contacts.

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