mineral

Selenite (Satin Spar)

Gypsum (CaSO4·2H2O)

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

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

Identified May 25, 2026More mineral →

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Physical properties

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

Formation & geological history

Formed as an evaporite mineral in sedimentary environments, often where saline lakes or seawater evaporate. Commonly found in massive beds or fibrous veins.

Uses & applications

Used in the manufacture of plaster of Paris, wallboard (drywall), and as a soil conditioner. Polished varieties like this are popular in the metaphysical community and for home decor.

Geological facts

Satin spar is often confused with 'true' selenite, which is transparent and plate-like. The Cave of the Crystals in Mexico contains giant selenite crystals over 30 feet long.

Field identification & locations

Identify by its extreme softness and its fibrous appearance that cat-eyes under light. Found globally, with major deposits in Morocco, Mexico, and the USA.