mineral
Raw selenite (gypsum)
Gypsum, CaSO₄·2H₂O; transparent varieties are called selenite
AI-generated identification · may be incorrectTypically colorless to white, pearly or vitreous, with prominent perfect cleavage and fibrous-to-tabular crystals; Mohs hardness 2, so it scratches easily with a fingernail. The specimen appears to be a translucent, cleavage-rich selenite chunk.
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Physical properties
Typically colorless to white, pearly or vitreous, with prominent perfect cleavage and fibrous-to-tabular crystals; Mohs hardness 2, so it scratches easily with a fingernail. The specimen appears to be a translucent, cleavage-rich selenite chunk.
Formation & geological history
Forms when evaporating saline water deposits calcium sulfate, commonly in sedimentary evaporite beds, caves, and clay-rich environments. Gypsum deposits range from recent to hundreds of millions of years old.
Uses & applications
Used chiefly in drywall, plaster, cement, soil amendment, and sculpture; clear attractive pieces are sold as display minerals. It is generally too soft for durable jewelry.
Geological facts
Selenite’s name references the Moon because of its luminous appearance; it is not a separate mineral species from gypsum. It can dissolve or become dull with prolonged water exposure.
Field identification & locations
Identify it by its very low hardness, light weight, silky/pearly luster, and easy cleavage into flat sheets; distinguish it from harder quartz, which will scratch glass. Major sources include Mexico, Morocco, Spain, the United States, and Australia.
