A number of ore shoot "outcrops" and surface expressions or criteria for ore shoots in the Southwest and northern Mexico are described. Safe generalizations on criteria that can be applied from one district to another seem to be limited because the variation in occurrence is large. The obvious method of attack where a district has produced ore is first to study the known ore shoots in their structural, lithologic, and mineralogical environment and then to search for similar frameworks in undeveloped areas. The work should include plane table methods of mapping on large scales, microscopical techniques and studies of the shapes of the ore shoots and the distribution of metals in the ore shoots and metalliferous zones. The quartz spectrograph should give valuable information in tying outcrops to ore shoots, but the high cost of the quantitative type of instruments limits their use in the field.

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