The Santa Eulalia Mining District, covering approximately 30 km2 is located 25 km east of the town of Chihuahua in the ierra Santo Domingo (Fig. 1). It is divided into two mineralized zones: the East Field (San Antonio Mine), and the West Field (Buena Tierra and Potosi Mines) (see Fig. 5). The orebodies are principally chimneys and mantos, consisting of minor filling and replacement along fractures and disseminated minerals in tactites.
Access to the district is by paved road from Chihuahua; a continually reconditioned dirt road runs for 11 km between the two fields. Temperatures in the dry steppe climate range from −4°C (winter low) to 38°C (summer high); the normal torrential rain period is from May to September with lighter rains in November and December. Mining is the region's main economic activity, employing about 90 percent of the working-age males; cattle-raising and agriculture are of domestic scale.