The Río Santa Maria Fluorite District lies at the Guanajuato–San Luis Potosí state line 100 km directly S50°E of the city of San Luis Potosí. The nearest important town is Río Verde 45 km N40°E away (Fig. 1). Access to the El Realito and El Refugio Mines is from Río Verde by a paved road for 16 km that turns southwest for 43 km to Alamos de Martinez at the center of the district. The nearest railroad station is Ciudad Fernandez, west of Río Verde.
The nearest seaport is Tampico on the Gulf of Mexico, 250 km east of Río Verde. The district covers 240 km2 and lies at the transition between the Sierra Madre Oriental and the Central Mesa (Fig. 1). The stratigraphy is presented on Table 1.