mineral

Satin Spar (Satin Spar Selenite)

Gypsum (CaSO4·2H2O)

Hardness: 2 on Mohs scale (can be scratched by fingernail). Color: White or pearly. Luster: Silky/satin-like. Crystal Structure: Monoclinic, typically found in fibrous, parallel bundles. Cleavage: Perfect in one direction.

Hardness: 2 on Mohs scale (can be scratched by fingernail)
Color: White or pearly
Luster: Silky/satin-like

Identified July 11, 2026More mineral →

Explore Satin Spar (Satin Spar Selenite) in the encyclopedia →

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 or in hydrothermal veins and clay beds. Specimens like this are frequently from the Cretaceous period.

Uses & applications

Commonly used in holistic and metaphysical practices (often mislabeled as 'selenite'), as decorative ornaments, and commercially in the production of plaster of Paris, drywall, and soil fertilizers.

Geological facts

While often sold as 'Selenite', true Selenite is the transparent variety of gypsum. Satin Spar is the fibrous variety shown here. It is highly soluble in water and should not be soaked. The world's largest gypsum crystals are found in the Naica Mine in Mexico.

Field identification & locations

Identify in the field by its extreme softness (scratches with a thumbnail) and its fibrous, silky luster. Common locations include Morocco, Mexico, USA (Utah), and various desert evaporite basins.

Other mineral specimens

See all

Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Sandstone with Mineral Veining or Crust

Sedimentary Sandstone (mostly SiO2 with Fe2O3 tinting)

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