mineral
Satin Spar (Gypsum)
Calcium Sulfate Dihydrate (CaSO4·2H2O)
Hardness: 2 on Mohs scale; Color: White to pearly; Luster: Silky to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in one direction; Specific gravity: 2.3
- Hardness
- 2 on Mohs scale
- Color
- White to pearly
- Luster
- Silky to pearly
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Physical properties
Hardness: 2 on Mohs scale; Color: White to pearly; Luster: Silky to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in one direction; Specific gravity: 2.3
Formation & geological history
Formed through the evaporation of seawater in massive prehistoric basins (evaporite) or by the hydration of anhydrite. This fibrous variety often forms in veins.
Uses & applications
Commonly used for ornamental carvings, palm stones, and decorative charging plates. The massive form is used in making plaster of Paris and drywall.
Geological facts
Satin spar is often mislabeled as 'Selenite' in the commercial market. While both are gypsum, selenite strictly refers to the transparent crystal form, while satin spar is the fibrous form.
Field identification & locations
Identifiable by its distinct silky luster and ability to be scratched by a fingernail. It should be kept away from water as it can dissolve or lose its luster over time.
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Schist
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Epidote
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metamorphic
Gypsum (variety Selenite or Alabaster)
Calcium sulfate dihydrate (CaSO4·2H2O)
Mineral
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Mineral/Rock
Granite
Granite (Phaneritic intrusive igneous rock)
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