mineral
Selenite gypsum crystal
Gypsum (CaSO₄·2H₂O), fibrous/selenite variety
AI-generated identification · may be incorrectColorless to white, transparent to translucent, vitreous to pearly luster, commonly bladed or fibrous with perfect {010} cleavage; Mohs hardness 2, specific gravity about 2.3. The specimen appears to be a slender, polished or naturally elongated blade.
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Physical properties
Colorless to white, transparent to translucent, vitreous to pearly luster, commonly bladed or fibrous with perfect {010} cleavage; Mohs hardness 2, specific gravity about 2.3. The specimen appears to be a slender, polished or naturally elongated blade.
Formation & geological history
Forms by evaporation of sulfate-rich water in sedimentary evaporite basins, saline lakes, caves, and hot-spring environments; deposits range from recent to Paleozoic and younger geological ages.
Uses & applications
Used to manufacture plaster, drywall, cement additives, and soil conditioners; clear crystals are popular inexpensive mineral specimens and may be used decoratively, though they are too soft for durable jewelry.
Geological facts
Selenite is not a separate mineral species but a transparent variety of gypsum. It can be scratched easily with a fingernail and dissolves slowly in water.
Field identification & locations
Identify by its very low hardness, light weight, perfect cleavage, and ability to split into thin sheets; common localities include Mexico, Spain, Morocco, the United States, and Australia. Avoid water, abrasion, and heat when collecting or displaying it.
