mineral

Selenite (Satin Spar)

Gypsum (Calcium Sulfate Dihydrate) - CaSO4·2H2O

Hardness: 2 on Mohs scale (can be scratched by a fingernail). Color: White, pearly. Luster: Vitreous to pearly/silky. Crystal structure: Monoclinic. Cleavage: Perfect one-directional cleavage. Specific gravity: 2.3.

Hardness: 2 on Mohs scale (can be scratched by a fingernail)
Color: White, pearly
Luster: Vitreous to pearly/silky

Identified June 29, 2026More mineral →

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Physical properties

Formation & geological history

Formed as an evaporite mineral in sedimentary environments such as saline lakes, lagoons, and hot springs. It can also form during the oxidation of sulfide ores.

Uses & applications

Used in the manufacture of plaster of Paris, wallboard (drywall), soil fertilizer, and as a decorative mineral for collectors and metaphysical uses.

Geological facts

The name 'Selenite' comes from the Greek word 'selene', meaning moon, referring to its pale, moon-like glow. The world's largest crystals are selenite, found in the Cave of the Crystals in Mexico.

Field identification & locations

Identify in the field by its extreme softness (scratches with a fingernail) and its fibrous, silky habit. Commonly found in Morocco, Mexico, and the Southwestern US. Collectors should handle with care as it is very fragile.

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

Gypsum (variety Selenite or Alabaster)

Calcium sulfate dihydrate (CaSO4·2H2O)

Mineral

Nephrite Jade

Nephrite

Mineral/Rock

Banded Gneiss (River Rock/Pebble)

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

Metamorphic Rock