mineral

Selenite (Satin Spar)

Gypsum (CaSO4·2H2O)

Hardness: 2 on Mohs scale (can be scratched by a fingernail). Color: Colorless to white/translucent. Luster: Pearly or silky. Crystal Structure: Monoclinic with perfect cleavage. Specific Gravity: 2.3.

Hardness: 2 on Mohs scale (can be scratched by a fingernail)
Color: Colorless to white/translucent
Luster: Pearly or silky

Identified May 2, 2026More mineral →

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Physical properties

Formation & geological history

Formed as an evaporite mineral in sedimentary environments such as dried lake beds, salt flats, and clay deposits. It precipitates from saline water during evaporation.

Uses & applications

Used extensively in the manufacture of wallboard (drywall), plaster of Paris, and soil conditioners. Large translucent crystals are prized by mineral collectors and the metaphysical community.

Geological facts

The name 'Selenite' is derived from the Greek 'selene' meaning moon, referring to the moon-like reflection from its cleavage faces. Giant selenite crystals up to 12 meters long exist in the Naica Mine in Mexico.

Field identification & locations

Identify in the field by its extreme softness (scratched by fingernail) and fibrous texture. Commonly found in Morocco, Mexico, and the southwestern United States (especially Utah and New Mexico).