These anhydrite crystals are from the Naica Mine in Naica, Mun. de Saucillo, Chihuahua, Mexico. It is mined for its deposits of silver, lead and zinc minerals. This mine also contains 87 different mineral species. The 50 foot selenite crystals in its “cave of swords” is worth mentioning. It is also famous for the unique blue colored anhydrite crystals found there. It is a sulfate that contains the elements Ca and S, and O. This piece consists of several interpenetrating, clusters of parallel anhydrite crystals. They are terminated at the top and have a chatoyant pearly luster. This piece measures 3 3/4 x 1 1/3 x 1 1/16 inches or 96 x 38 x 26 mm.