mineral

Selenite (Satin Spar)

Calcium Sulfate Dihydrate (CaSO4·2H2O)

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

Hardness: 2 on Mohs scale (can be scratched by a fingernail)
Color: White or colorless
Luster: Pearly or silky

Identified June 25, 2026More mineral →

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Physical properties

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.

Other mineral specimens

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Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Schist

Metamorphic

Epidote

Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)

metamorphic

Nephrite Jade

Nephrite

Mineral/Rock

Banded Gneiss (River Rock/Pebble)

Gneiss (specifically a banded variety often found as a river rock)

Metamorphic Rock

Green Apatite on Albite

Fluorapatite [Ca5(PO4)3F] on Albite [Na(AlSi3O8)]

mineral