mineral
Selenite (Satin Spar)
Gypsum (CaSO4·2H2O)
Hardness: 2 (Mohs); Color: White, translucent; Luster: Pearly, silky; Crystal System: Monoclinic; Cleavage: Perfect; Specific Gravity: 2.3
- Hardness
- 2 (Mohs)
- Color
- White, translucent
- Luster
- Pearly, silky
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Physical properties
Hardness: 2 (Mohs); Color: White, translucent; Luster: Pearly, silky; Crystal System: Monoclinic; Cleavage: Perfect; Specific Gravity: 2.3
Formation & geological history
Formed as an evaporite mineral in sedimentary basins from the evaporation of saline waters, often found in ancient sea beds.
Uses & applications
Used in plaster of Paris, drywall (as gypsum), spiritual/metaphysical collecting, and as ornamental carved pieces.
Geological facts
Satin spar is a fibrous variety of gypsum that exhibits a 'cat's eye' chatoyancy. It is extremely soft and can be scratched with a fingernail.
Field identification & locations
Look for silk-like fibrous parallel structures. It is very soft and water-soluble; do not soak in water as it will eventually dissolve.
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Other mineral specimens
Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Sandstone with Mineral Veining or Crust
Sedimentary Sandstone (mostly SiO2 with Fe2O3 tinting)
sedimentary
Schist
Schist
Metamorphic
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Gypsum (variety Selenite or Alabaster)
Calcium sulfate dihydrate (CaSO4·2H2O)
Mineral
Nephrite Jade
Nephrite
Mineral/Rock