mineral
Selenite (Satin Spar)
Calcium Sulfate Dihydrate (CaSO4·2H2O)
AI-generated identification · may be incorrectHardness: 2 on Mohs scale (can be scratched by a fingernail); Color: White or colorless; Luster: Pearly or silky; Crystal Structure: Monoclinic; Cleavage: Perfect in one direction; Specific Gravity: 2.3
- Hardness
- 2 on Mohs scale (can be scratched by a fingernail)
- Color
- White or colorless
- Luster
- Pearly or silky
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Physical properties
Hardness: 2 on Mohs scale (can be scratched by a fingernail); Color: White or colorless; Luster: Pearly or silky; Crystal Structure: Monoclinic; Cleavage: Perfect in one direction; Specific Gravity: 2.3
Formation & geological history
Formed as an evaporite mineral in alkaline lake muds, clay beds, and salt flats. It originates from the evaporation of seawater in prehistoric basins.
Uses & applications
Used in the manufacturing of plaster of Paris, drywall, and fertilizer. In decorative form, it is used for carvings, lamps, and as a popular metaphysical or 'cleansing' stone for collectors.
Geological facts
True Selenite is transparent, but the fibrous 'Satin Spar' variety shown here is what most people call Selenite. It is name after the Greek goddess of the moon (Selene) due to its moon-like glow.
Field identification & locations
Identified by its extreme softness and fibrous, 'chatoyant' appearance. It is water-soluble and will eventually dissolve if left in water. Common in Morocco, Mexico, and the USA.
