mineral
Satin Spar (Gypsum)
Hydrous Calcium Sulfate (CaSO4·2H2O)
AI-generated identification · may be incorrectHardness: 2 (Mohs scale), Color: White to pearly cream, Luster: Silky/Satin, Crystal Structure: Monoclinic, Cleavage: Perfect, Specific Gravity: 2.3
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Physical properties
Hardness: 2 (Mohs scale), Color: White to pearly cream, Luster: Silky/Satin, Crystal Structure: Monoclinic, Cleavage: Perfect, Specific Gravity: 2.3
Formation & geological history
Formed in evaporite deposits where saline water evaporates, or by the hydration of anhydrite. Found in sedimentary environments such as lake and marine beds.
Uses & applications
Used in the manufacture of drywall (plasterboard), cement, fertilizer, and as an ornamental stone for carvings and decorative items.
Geological facts
Satin spar is a fibrous variety of gypsum. It is often confused with Selenite, which is the clear, crystalline form, though both are chemically identical. It is so soft it can be easily scratched by a fingernail.
Field identification & locations
Identify by its silky, fibrous appearance and extreme softness (can be scratched by a human fingernail). Commonly found in desert regions or ancient seabed locations like Utah, Morocco, and Mexico.
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