mineral

Selenite (Satin Spar)

Gypsum (Calcium Sulfate Dihydrate, CaSO4·2H2O)

Hardness: 2 on Mohs scale (can be scratched by a fingernail). Color: White or pearly. Luster: Silky/Satin. Crystal structure: Monoclinic, often fibrous. Cleavage: Perfect in one direction.

Hardness: 2 on Mohs scale (can be scratched by a fingernail)
Color: White or pearly
Luster: Silky/Satin

Identified June 2, 2026More mineral →

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Physical properties

Hardness: 2 on Mohs scale (can be scratched by a fingernail). Color: White or pearly. Luster: Silky/Satin. Crystal structure: Monoclinic, often fibrous. Cleavage: Perfect in one direction.

Formation & geological history

Formed from the evaporation of ancient seawater in saline basins (evaporite) and through hydrothermal activity. Found in sedimentary environments worldwide.

Uses & applications

Used in the manufacture of drywall (gypsum board), plaster of Paris, fertilizer, and as a popular decorative crystal in metaphysical and mineral collections.

Geological facts

Satin spar is the fibrous variety of selenite that exhibits a shimmering effect called chatoyancy. Its name comes from the Greek word 'selene' meaning 'moon,' due to its pearly glow.

Field identification & locations

Identify by its extreme softness (scratches with a fingernail) and fibrous texture. Often found in dry lake beds or as veins in clay and limestone. Keep away from water as it can erode over time.

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