In New Mexico, there are at least 100,000 abandoned mine waste rock piles with widely ranging geochemical and mineralogical compositions. A geochemical
and mineralogical study was implemented for five waste rock piles, some which contained sulfides, in the Hillsboro Mining District. Chemical and physical
characteristics of mineral grains and their secondary mineral oxidation rinds were examined with the electron microprobe. Pyrite and chalcopyrite appear to be
the most reactive to oxidizing conditions. Clays, iron oxide, iron hydroxide, iron sulfate, and primary texture rinds exist in the waste rock piles analyzed.