mineral

Satin Spar (Selenite)

Gypsum (Calcium Sulfate Dihydrate) - CaSO4·2H2O

Hardness: 2 on Mohs scale (can be scratched by a fingernail). Color: White or pearly. Luster: Silky or pearlescent. Crystal structure: Monoclinic, typically fibrous. Cleavage: Perfect in one direction. Specific gravity: 2.3.

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

Identified March 22, 2026More mineral →

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Physical properties

Formation & geological history

Formed as an evaporite mineral in sedimentary environments, often in marine basins or salt lakes where water has evaporated. It can also form through the oxidation of sulfide ores.

Uses & applications

Commonly used for ornamental carvings, decorative 'wands' in the metaphysical community, and historically in the production of plaster of Paris and drywall.

Geological facts

Satin spar is often confused with true Selenite (which is transparent). It is famous for its optical properties where light reflects off the fibrous structure, creating a 'cat's eye' or chatoyant effect.

Field identification & locations

Identify in the field by its extreme softness (scratches easily) and fibrous, silky appearance. Frequently found in Morocco, Mexico, and the USA (Utah/New Mexico). Collectors should avoid water as it can dissolve or dull the surface over time.

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