This selenite is from Santa Eulalia in the Mun. de Aquiles Serdan, Chihuahua, Mexico. This district encompasses a large area that contains over a dozen mines. Mining activities are primarily for the extraction of silver and other metals. There a over 150 different types of minerals in the district including selenite. It is a sulfate that contains the elements Ca, S, H and O. This specimen is made up entirely of fibrous elongated selenite crystals that form a lightly curved and twisted formation This piece measures 6 1/8 x 1 1/8 x 9/16 inches or 156 x 28 x 14 mm at its largest dimensions.