A gypsum cave is a natural karstic formation in gypsum. Gypsum karst is very rare. It depends on deposits of gypsum or anhydrite, often also called alabaster. Chemically it is calcium sulfate, CaSO4. Gypsum caves can be found in several places on earth, including: Optymistychna Cave in Ukraine, considered the longest gypsum cave at 232 km Orda Cave underneath the Western Ural Mountains, with 5.1km length, including 4.8km underwater Cuevas de Sorbas in Almeria, Spain Caves noted for large scale gypsum speleothems include: Cave of the Crystals in Chihuahua, Mexico Lechuguilla Cave in New Mexico, US References Related pages Gypsum Karst External links World's longest gypsum caves compiled Gypsum caves Landforms Geomorphology