mineral

Selenite (gypsum crystal)

Gypsum, CaSO₄·2H₂O; monoclinic crystal

AI-generated identification · may be incorrect

Pale cream to white, pearly or silky luster, and conspicuous lengthwise striations; hardness 2 Mohs, perfect cleavage, and relatively low specific gravity (~2.3).

Identified October 3, 2026More mineral →

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Physical properties

Pale cream to white, pearly or silky luster, and conspicuous lengthwise striations; hardness 2 Mohs, perfect cleavage, and relatively low specific gravity (~2.3).

Formation & geological history

Forms when calcium- and sulfate-rich waters evaporate, commonly in sedimentary basins and evaporite deposits. Gypsum deposits span many geological ages; the specimen’s age and locality cannot be determined from the image.

Uses & applications

Gypsum is used to make plaster, drywall, and cement; clear selenite crystals are collected and sometimes carved or used decoratively.

Geological facts

Gypsum is soft enough to scratch with a fingernail and can be scratched by a copper coin; it is not the same mineral as satin spar, though both are gypsum varieties.

Field identification & locations

The elongated, fibrous-looking crystal habit and soft, pale surface are consistent with gypsum. Common deposits occur in evaporite settings worldwide; avoid water and rough handling because gypsum is soft and can cleave or flake.