mineral
Raw selenite (gypsum)
Gypsum, CaSO₄·2H₂O; transparent varieties are called selenite
AI-generated identification · may be incorrectMohs hardness 2, colorless to white with pearly or glassy luster, excellent one-directional cleavage, commonly tabular or fibrous crystals, and specific gravity about 2.3. The specimen appears translucent, cleavable, and probably natural or lightly shaped.
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Physical properties
Mohs hardness 2, colorless to white with pearly or glassy luster, excellent one-directional cleavage, commonly tabular or fibrous crystals, and specific gravity about 2.3. The specimen appears translucent, cleavable, and probably natural or lightly shaped.
Formation & geological history
Forms when evaporating saline water precipitates calcium sulfate, and also occurs in sedimentary evaporite beds, caves, and hydrothermal settings. Deposits range from ancient to modern geological ages.
Uses & applications
Used to manufacture plaster, drywall, cement additives, and soil conditioners; clear attractive pieces are sold as decorative or metaphysical specimens. It is generally too soft for durable jewelry.
Geological facts
Selenite is easily scratched by a fingernail and can be damaged or dissolved by prolonged water exposure. The name derives from Selene, the Greek Moon goddess, because of its moonlike sheen.
Field identification & locations
Common localities include Mexico, Morocco, the United States, Spain, and Brazil; the large desert crystals of Naica, Mexico, are famous. Confirm with fingernail softness, perfect cleavage, and lack of fizz in dilute acid; do not use a destructive test on display pieces.
