mineral
White gypsum (likely selenite/alabaster)
Gypsum, CaSO₄·2H₂O
AI-generated identification · may be incorrectWhite, translucent-to-opaque piece with a pearly/satiny luster and likely fibrous or platy texture. Mohs hardness 2; monoclinic crystals, with perfect cleavage in one direction; specific gravity about 2.3.
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Physical properties
White, translucent-to-opaque piece with a pearly/satiny luster and likely fibrous or platy texture. Mohs hardness 2; monoclinic crystals, with perfect cleavage in one direction; specific gravity about 2.3.
Formation & geological history
Gypsum forms when calcium-sulfate-rich water evaporates in sedimentary basins, often alongside halite. Deposits range from recent to hundreds of millions of years old; the image alone cannot establish age or confirm the variety.
Uses & applications
Used to make plaster and drywall and as a soil amendment; translucent selenite is also collected and used decoratively.
Geological facts
Gypsum is soft enough to be scratched with a fingernail and can be carved easily.
Field identification & locations
Check for a fingernail scratch and a white streak; gypsum commonly occurs in evaporite deposits worldwide. The specimen’s rough, white appearance is consistent with gypsum, but a photo cannot confirm identification.
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