mineral

Satin Spar (Selenite)

Gypsum (Calcium Sulfate Dihydrate) - CaSO4·2H2O

Hardness: 2 on Mohs scale (can be scratched by a fingernail). Color: White or colorless. Luster: Pearly or silky (satin-like). Crystal structure: Monoclinic, typically fibrous. 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 (satin-like)

Identified April 28, 2026More mineral →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed as an evaporite mineral in sedimentary environments, typically from the evaporation of seawater or saline lake water. It can also form through the hydration of anhydrite or in hydrothermal veins.

Uses & applications

Commonly used for decorative carvings, crystal healing, and metaphysical practices. Industrially, gypsum is essential for making drywall (plasterboard), cement, and soil conditioners in agriculture.

Geological facts

While often sold and referred to as 'Selenite' in trade, this specific fibrous variety is technically Satin Spar. True Selenite is transparent and platelike. It is one of the softest minerals and is soluble in water over long periods.

Field identification & locations

Identify in the field by its extreme softness (scratched by a fingernail) and fibrous, silky appearance. Commonly found in Morocco, Mexico, and the USA (Utah/New Mexico). Collectors should avoid getting it wet.

Other mineral specimens

See all

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