Gypsum from Great Salt Plains, Oklahoma, USA

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Classic material for the species and locality, and aesthetic large grouping of gypsum crystals with attached sand. In excellent condition all around and no points of attachment. The Great Salt Plains, located near Jet in Alfalfa County, Oklahoma, are a unique geological landmark formed from the remnants of an ancient Permian inland sea. Geologically, the flats consist of extensive salt and gypsum deposits left behind by repeated evaporation cycles, maintained by shallow, highly mineralized groundwater that continually brings saline brines to the surface. Mineralogically, the area is world-famous for producing hourglass selenite, a rare variety of gypsum crystal characterized by transparent, bladed crystal forms enclosing distinct, dark hourglass-shaped patterns of trapped sand and clay. Historically, the region gained widespread attention during the early-to-mid 20th century for its unusual subterranean mineral growth, leading to the establishment of the Salt Plains National Wildlife Refuge, where visitors are legally permitted to dig for these unique gypsum crystals.