mineral
Selenite tower
Selenite (transparent to translucent gypsum), CaSO₄·2H₂O
AI-generated identification · may be incorrectMohs hardness 2; white to colorless, pearly or vitreous luster, monoclinic crystals, and perfect one-directional cleavage. The elongated polished form shows fibrous satin-spar texture and translucency.
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Physical properties
Mohs hardness 2; white to colorless, pearly or vitreous luster, monoclinic crystals, and perfect one-directional cleavage. The elongated polished form shows fibrous satin-spar texture and translucency.
Formation & geological history
Forms when evaporating saline or groundwater precipitates hydrated calcium sulfate, commonly in sedimentary evaporite beds; individual crystals may grow over thousands to millions of years. This specimen has been cut and polished into a tower.
Uses & applications
Used decoratively and collected for its glow and fibrous texture; gypsum is widely used in drywall, plaster, cement, and fertilizer. Selenite is generally too soft for durable jewelry.
Geological facts
Despite its glasslike appearance, it is very soft and scratches easily with a fingernail. “Selenite” is a variety name for clear or translucent gypsum, not a separate mineral species.
Field identification & locations
Identify by its white translucency, silky fibers, softness, and easy cleavage; avoid water because prolonged exposure can dull or dissolve the surface. Common sources include Morocco, Mexico, the United States, and Spain.
