mineral

Satin Spar (Gypsum)

Calcium Sulfate Dihydrate (CaSO4·2H2O)

Hardness: 2 (can be scratched by a fingernail); Color: Pearly white to translucent; Luster: Silky or pearly; Crystal structure: Monoclinic; Cleavage: Perfect in one direction

Hardness: 2 (can be scratched by a fingernail)
Color: Pearly white to translucent
Luster: Silky or pearly

Identified April 7, 2026More mineral →

Identify your own rocks.

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

App Store Google Play

Physical properties

Hardness: 2 (can be scratched by a fingernail); Color: Pearly white to translucent; Luster: Silky or pearly; Crystal structure: Monoclinic; Cleavage: Perfect in one direction

Formation & geological history

Formed as an evaporite mineral in sedimentary environments, typically where salt water or mineral-rich ground water evaporates. Most deposits formed during the Triassic or Permian periods.

Uses & applications

Used in drywall construction (plasterboard), as a soil conditioner in agriculture, and as a popular ornamental stone for carvings and metaphysical use.

Geological facts

Satin spar is often mislabeled as 'Selenite' in the commercial market. While both are gypsum, satin spar is characterized by its fibrous, silky habit, whereas true selenite is transparent and platy.

Field identification & locations

Identify in the field by its very low hardness (scratched by fingernail) and fibrous, silky texture. Commonly found in desert regions with ancient lake beds or near sulfur springs.

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