mineral

Selenite (Satin Spar)

Gypsum (CaSO4·2H2O)

Hardness: 2 on Mohs scale (can be scratched by a fingernail). Color: White or colorless. Luster: Pearly or silky (satin-like). Crystal structure: Monoclinic; often fibrous. Cleavage: Perfect in one direction.

Hardness: 2 on Mohs scale (can be scratched by a fingernail)
Color: White or colorless
Luster: Pearly or silky (satin-like)

Identified May 5, 2026More mineral →

Explore Selenite (Satin Spar) in the encyclopedia →

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Physical properties

Formation & geological history

Forms in evaporite environments where saltwater evaporates, leaving behind concentrated calcium sulfate. Often found in sedimentary clay beds or near dried-up prehistoric lake beds.

Uses & applications

Used in drywall and plaster of Paris for construction, as a soil conditioner in agriculture, and widely sold as physical decorative pieces or for metaphysical/meditation use.

Geological facts

The name Selenite comes from the Greek word 'selene' meaning moon, referring to its pale, moon-like glow. The famous Naica Cave of Crystals in Mexico contains selenite crystals up to 39 feet long.

Field identification & locations

Identify in the field by its extreme softness and its fibrous, 'stair-step' fracture pattern. Found globally in gypsum deposits, particularly in the USA, Morocco, and Mexico.