The Tejocotes mines in the state of Oaxaca have produced more antimony per year since 1938 than any other area in Mexico. Average annual production from 1938 to 1943 was 4,300 metric tons of shipped ores containing 56 to 58 percent of metallic antimony (Fig. 1).
The mid-Jurassic complexly folded and faulted sedimentary section comprises three limestone and three shale formations, all overlain by sandstones and affected by quartz and feldspar porphyry intrusions.
The antimony deposits occur in limestones as: (1) irregular or roughly elongate orebodies, (2) similarly shaped masses in argillaceous material that replaced the limestone, (3) fracture-fill veins, and (4) veinlets or disseminated masses. Types 1 and 2 are found near and generally more or less parallel to the quartz porphyry contacts. Each orebody averages several tons of mineral for export, and some attain 500 tons.