The Velardeña Mining Unit, owned by Minerales Metálicos del Norte, S.A., a member of Grupo Industrial Minera México, S.A. de C.V., is located in northeastern Durango State within the Cuencamé municipality, 150 km northeast of the city of Durango and 85 km south-southwest of Torreón. Geographic coordinates of Velardeña Village, in the vicinity of the mineworks, are 25°04′N and 103°44′W. Altitude above sea level ranges from 1,400 m in the valley separating Sierra de Santa Maria and Sierra de San Lorenzo to about 2,000 m at the San Lorenzo peaks. Climate and vegetation are typical of northern Mexico’s semidesert zone. Federal Highway 49 runs approximately 6 km northwest of Velardeña, crossing the Durango-TorreÃ³n railroad track 2.5 km farther on at PedriceÃ±a, near which is a small light-aircraft runway. Velardeña has telephone and telegraph facilities, schools, and other services for a population of 5,000, most of whom depend on the mines for a living (Fig. 1).