mineral
Satin Spar (Gypsum)
Calcium Sulfate Dihydrate (CaSO4·2H2O)
Hardness: 2 on Mohs scale; Color: Grayish-white, translucent; Luster: Silky to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in one direction, displaying fine fibrous parallel striations.
- Hardness
- 2 on Mohs scale
- Color
- Grayish-white, translucent
- Luster
- Silky to pearly
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Physical properties
Hardness: 2 on Mohs scale; Color: Grayish-white, translucent; Luster: Silky to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in one direction, displaying fine fibrous parallel striations.
Formation & geological history
Formed as an evaporite mineral in lake and marine settings where mineral-rich water evaporates, or through hydrothermal deposition in veins.
Uses & applications
Used widely in ornamental carvings, polished wand/slabs for metaphysical crystal collecting, plaster manufacture, and drywall production.
Geological facts
Satin spar is often mistakenly sold as 'selenite'. While both are varieties of gypsum, satin spar exhibits a fibrous structure that gives it a silky luster and chatoyancy (cat's-eye effect), whereas selenite forms clear, flat, sheet-like crystals.
Field identification & locations
Can be identified by its soft surface easily scratched by a fingernail and distinct parallel fibrous texture. Commonly found in Morocco, USA, Mexico, and England.
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Calcium sulfate dihydrate (CaSO4·2H2O)
Mineral