mineral

Satin Spar (often sold as Selenite)

Gypsum (CaSO4·2H2O)

Hardness: 2 on Mohs scale; Color: White or colorless; Luster: Pearly or silky (chatoyant); Crystal structure: Monoclinic; Cleavage: Perfect in one direction; Specific gravity: 2.3

Hardness: 2 on Mohs scale
Color: White or colorless
Luster: Pearly or silky (chatoyant)

Identified May 13, 2026More mineral →

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Physical properties

Hardness: 2 on Mohs scale; Color: White or colorless; Luster: Pearly or silky (chatoyant); Crystal structure: Monoclinic; Cleavage: Perfect in one direction; Specific gravity: 2.3

Formation & geological history

Formed as an evaporite mineral in sedimentary environments such as saline lakes, lagoons, and deep caves where sulfate-rich waters evaporate.

Uses & applications

Commonly used for ornamental carvings, palm stones, and decorative items. In industrial forms, gypsum is used for plaster, drywall, and fertilizer.

Geological facts

While commonly called 'Selenite' in the crystal trade, this fibrous variety is scientifically known as 'Satin Spar.' It is so soft that it can be scratched with a fingernail.

Field identification & locations

Identify by its extreme softness and silky, fibrous appearance. Commonly found in Morocco, Mexico, and the USA. Keep away from water as it can dissolve or degrade over time.

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