mineral

Gypsum (selenite)

Gypsum, CaSO₄·2H₂O

AI-generated identification · may be incorrect

Colorless to pale honey, transparent-to-translucent, vitreous to pearly, with prominent cleavage and a likely fibrous or striated texture. Mohs hardness 2; monoclinic crystal system; specific gravity about 2.3. The photo alone cannot confirm the identification.

Identified October 10, 2026More mineral →

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Physical properties

Formation & geological history

Gypsum forms when sulfate-rich water evaporates in sedimentary basins, and also occurs in veins and caves. 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, though its softness limits jewelry use.

Geological facts

Gypsum is soft enough to scratch with a fingernail and can be scratched by a copper coin.

Field identification & locations

Check for very low hardness and a white streak; selenite commonly occurs in evaporite deposits alongside halite and anhydrite. Common localities include Mexico, the United States, and Spain.