mineral

Satin Spar (often marketed as Selenite)

Gypsum (Calcium Sulfate Dihydrate) - CaSO4·2H2O

Hardness: 2 on Mohs scale (can be scratched by a fingernail); Color: Translucent white with pearly/silky sheen; Luster: Vitreous to pearly; Crystal structure: Monoclinic with fibrous growth; Cleavage: Perfect in one direction; Specific Gravity: 2.3

Hardness: 2 on Mohs scale (can be scratched by a fingernail)
Color: Translucent white with pearly/silky sheen
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 such as saline lakes or lagoons where sulfate-rich water evaporates. It can form in various geological ages but is common in Permian and Triassic deposits.

Uses & applications

Primarily used in the 'metaphysical' industry for carvings, lamps, and palm stones. Industrially, gypsum is used in dry wall, plaster of Paris, and as a soil conditioner (fertilizer).

Geological facts

While commonly called 'Selenite' by retailers, this fibrous variety is technically 'Satin Spar.' It is so soft that it is water-soluble over long periods of time; putting it in a salt bath or water can damage the surface of the specimen.

Field identification & locations

Identify in the field by its extreme softness and fibrous, 'cat's eye' (chatoyant) light reflection. Commonly found in Morocco, Mexico, and the USA (Utah/New Mexico). Collectors can identify it by the fact it feels warmer to the touch than glass or quartz due to low thermal conductivity.

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