mineral

Selenite (gypsum)

Gypsum, CaSO₄·2H₂O; transparent or translucent variety commonly called selenite

AI-generated identification · may be incorrect

Very soft (Mohs 2), white to colorless, pearly to vitreous luster, and commonly forms clear, bladed or tabular monoclinic crystals with perfect cleavage. The block appears translucent and cleavage-shaped, though its exact variety is uncertain from the image.

Identified August 15, 2026More mineral →

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Physical properties

Formation & geological history

Forms through evaporation of sulfate-rich seawater or lake water, and in sedimentary evaporite beds, hot-spring deposits, and cavities. Gypsum deposits range from ancient Paleozoic evaporites to modern deposits.

Uses & applications

Used to manufacture plaster, drywall, cement additives, and soil conditioners; clear specimens are sold as decorative minerals. It is generally unsuitable for jewelry because it scratches and dissolves relatively easily.

Geological facts

Selenite is not a separate mineral species but a transparent gypsum variety; the name references Selene, the Moon. It can be scratched easily with a fingernail and may become dull or damaged by water and abrasion.

Field identification & locations

Common localities include Mexico, Morocco, Spain, the United States, and Brazil. Confirm with a fingernail scratch, low density, and excellent cleavage; distinguish it from calcite, which is harder and reacts with dilute acid.