mineral
Gypsum (selenite)
Gypsum, CaSO₄·2H₂O; likely a translucent, bladed selenite crystal
AI-generated identification · may be incorrectMohs hardness 2; colorless to pale gray with yellow-brown staining; vitreous to pearly luster, monoclinic crystals, and perfect cleavage. The specimen appears as thin, translucent blades, but exact identification from the photo is uncertain.
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Physical properties
Mohs hardness 2; colorless to pale gray with yellow-brown staining; vitreous to pearly luster, monoclinic crystals, and perfect cleavage. The specimen appears as thin, translucent blades, but exact identification from the photo is uncertain.
Formation & geological history
Forms when calcium- and sulfate-rich water evaporates in sedimentary basins; gypsum deposits range from recent to hundreds of millions of years old.
Uses & applications
Used to make plaster, drywall, and cement; clear selenite is collected and sometimes carved into ornaments.
Geological facts
Gypsum is soft enough to scratch with a fingernail and can be scratched by a copper coin.
Field identification & locations
Look for very soft, pale, often bladed crystals and a white streak; common in evaporite deposits worldwide. A small specimen like this typically sells for about $2–$15 USD, depending on clarity and provenance.
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