History and geology of the precious metal occurrences in Socorro County, New Mexico
— Robert M. North

Precious metals, in varying degrees of importance, have been reported from 21 mining districts in Socorro County (fig. 1). Most of these occurrences have little or no reported production, but all are included to present a complete overall picture of the occurrence of precious metals in the county. Space limitations preclude an exhaustive discussion of each occurrence here; however, comprehensive references are given.

For the purpose of this discussion, an "occurrence" of precious metals is defined as a deposit (no size restriction) with precious metal contents of at least 100 times average crustal abundance. The average crustal abundance of gold is approximately 0.005 ppm (0.00015 oz/ ton) and silver approximately 0.070 ppm (0.0020 oz/ton). No platinum or platinum group metals are known to occur in the county. Since no complete geochemical study of the county has been made, the occurrences discussed are limited to areas that have been previously prospected or mined for base or precious metals.

The precious metal occurrences of the county can be separated into four groups: (1) veins associated with Tertiary subaerial olcanic rocks; (2) replacement, vein, and skarn deposits associated with Tertiary intrusive rocks; (3) deposits in Paleozoic sedimentary rocks that are not obviously associated with igneous activity; and (4) deposits of uncertain age or origin.