mineral

Satin Spar (Selenite)

Gypsum (Calcium Sulfate Dihydrate) - CaSO4·2H2O

Hardness: 2 on Mohs scale (can be scratched with a fingernail); Color: Pearly white or colorless; Luster: Silky to pearly; Crystal structure: Monoclinic with fibrous habit; Cleavage: Perfect in one direction; Specific gravity: 2.3

Hardness: 2 on Mohs scale (can be scratched with a fingernail)
Color: Pearly white or colorless
Luster: Silky 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 a sedimentary evaporite mineral in saline lakes, lagoons, and caves during the evaporation of seawater; occurs in strata from various geological ages, often associated with limestone or shale.

Uses & applications

Used primarily for ornamental carvings, palm stones, and decorative towers in the metaphysical industry. Industrial gypsum is used for plaster, drywall, and soil fertilizer; however, this fibrous form is mostly for collectors.

Geological facts

Named after the Greek goddess of the moon (Selene) due to its moon-like glow. It is chemically identical to Alabaster and Desert Rose but differs in crystal habit. The Naica Crystal Cave in Mexico houses some of the world's largest selenite crystals.

Field identification & locations

Identify in the field by its extreme softness (scratch with a nail) and its chatoyancy (cat's eye effect) when light hits the fibers. Common locations include Morocco, Mexico, USA (Utah), and Brazil. Collectors should keep it dry as it is slightly water-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