mineral

Selenite (gypsum)

Gypsum, CaSO₄·2H₂O; variety commonly called satin spar or selenite

AI-generated identification · may be incorrect

White, translucent, pearly-to-vitreous luster with prominent cleavage; monoclinic crystals, Mohs hardness 2, specific gravity about 2.3. The block appears cut or polished and may be satin spar gypsum rather than a natural crystal termination.

Identified August 11, 2026More mineral →

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Physical properties

Formation & geological history

Forms by evaporation in sedimentary evaporite basins, hot springs, and veins; deposits range from modern to Paleozoic and younger geological ages. This specimen is human-shaped or cut from massive gypsum.

Uses & applications

Used for plaster, drywall, cement, soil amendment, and casts; clear or attractive pieces are sold as décor, healing-stone objects, and mineral specimens.

Geological facts

Gypsum is soft enough to scratch with a fingernail and can be flexed when occurring as thin fibers. “Selenite” technically refers to clear crystalline gypsum, while satin spar is fibrous gypsum.

Field identification & locations

Identify by its very low hardness, white color, perfect cleavage, and lack of fizz in dilute acid; avoid soaking, as gypsum can dissolve or become damaged. Common sources include Mexico, Morocco, Spain, the United States, and Australia.