mineral

Satin Spar Selenite (Gypsum)

Calcium sulfate dihydrate (CaSO4·2H2O)

Hardness: 2 on Mohs scale (can be scratched by a fingernail); Color: white or translucent with a pearly or silky luster; Crystal structure: Monoclinic; Cleavage: Perfect in one direction; Specific gravity: 2.3

Hardness: 2 on Mohs scale (can be scratched by a fingernail)
Color: white or translucent with a pearly or silky luster

Identified June 28, 2026More mineral →

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Physical properties

Formation & geological history

Formed as an evaporite mineral in sedimentary environments, typically where salt water has evaporated. It often forms in prehistoric lake and ocean beds. Geological age varies greatly by location.

Uses & applications

Used primarily for ornamental carvings, interior decoration, and holistic/metaphysical collecting. Gypsum in general is used in drywall, plaster, and as a fertilizer.

Geological facts

Satin spar is a fibrous variety of gypsum that exhibits chatoyancy, or the 'cat's eye' effect, when light reflects off its internal fibers. It is often confused with true Selenite, which is the transparent, plate-like form of gypsum.

Field identification & locations

Identify in the field by its extreme softness (scratchable by fingernail) and silky, fibrous appearance. Commonly found in desert regions like the Southwestern US, Morocco, and Mexico.

Other mineral specimens

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Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

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

Banded Gneiss (River Rock/Pebble)

Gneiss (specifically a banded variety often found as a river rock)

Metamorphic Rock