mineral

Satin Spar (Gypsum)

Calcium Sulfate Dihydrate (CaSO4·2H2O)

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

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

Identified April 5, 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 with fibrous growth habit; Cleavage: Perfect in one direction.

Formation & geological history

Formed as an evaporite mineral in sedimentary environments, typically from the evaporation of seawater or in saline lakes. It can also form as a secondary mineral in volcanic regions or through the hydration of anhydrite.

Uses & applications

Used in the production of plaster of Paris, wallboard (drywall), soil fertilizer, and ornamental carvings. Common in metaphysical 'healing' stone markets.

Geological facts

Satin spar is often confused with the more expensive mineral Selenite; while both are gypsum, satin spar is fibrous whereas selenite is transparent and crystalline. It is so soft that it is extremely easy to carve but also easily damaged.

Field identification & locations

Identify in the field by its distinctive silky luster and low hardness (scratches easily with a fingernail). Commonly found in areas with ancient seabed deposits such as Morocco, Mexico, and the Southwestern USA.

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