mineral

Selenite (Gypsum Variety)

Hydrous Calcium Sulfate (CaSO4·2H2O)

Hardness: 2 on Mohs scale (scratchable by fingernail). Color: Colorless to white. Luster: Vitreous to pearly. Crystal structure: Monoclinic with distinct tabular or bladed habits. Cleavage: Perfect in one direction (micaceous). Specific gravity: 2.3.

Hardness: 2 on Mohs scale (scratchable by fingernail)
Color: Colorless to white
Luster: Vitreous to pearly

Identified March 16, 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, often resulting from the evaporation of seawater in prehistoric basins. It can also form through the hydration of anhydrite or via hydrothermal veins.

Uses & applications

Used in the manufacture of drywall (gypsum board), plaster of Paris, and soil conditioners. In jewelry and collecting, it is valued for its pearly aesthetic, though it is often kept as raw specimens due to its extreme fragility.

Geological facts

Selenite is named after the Greek word 'selene' (Moon) because of its moon-like glow. The famous 'Cave of the Crystals' in Naica, Mexico, contains giant selenite crystals measuring up to 12 meters long.

Field identification & locations

Identify in the field by its softness (it can be scratched with a thumbnail) and its tendency to peel into thin, flexible but non-elastic sheets. Commonly found in desert regions (evaporite beds) and near hot springs. Collectors should store it in dry containers away from water, as it is slightly soluble.

Other mineral specimens

See all

Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

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

Epidote

Epidote - Ca2(Al2,Fe3+)3(SiO4)3(OH)

mineral