The Charcas Mining District is located about 110 km north of the city of San Luis Potosí at geographic coordinates 23°07′N and 101°06′W, with an average altitude of 2,200 m. The climate is temperate and semiarid; annual precipitation averages 450 mm.
Access is by a paved road that extends north for 80 km from Highway 57, and by 130 km of paved road leading south to San Luis Potosí; the México-Laredo Railroad runs 13 km east of the district (Fig. 1), which also has a light-aircraft runway. Local schools reach technical and preparatory levels.
Mining is the main economic activity followed by cattle raising, trade, and agriculture. Present population is 25,000, of which 1,300 family groups depend directly on the mining activity for a livelihood.