mineral

Satin Spar (Gypsum)

Hydrous Calcium Sulfate (CaSO4·2H2O)

Hardness: 2 on Mohs scale (scratchable by a fingernail). Color: White or pearly. Luster: Silky or pearly luster. Crystal Structure: Monoclinic; often found in fibrous, parallel bundles. Cleavage: Perfect in one direction and distinct in two others.

Hardness: 2 on Mohs scale (scratchable by a fingernail)
Color: White or pearly
Luster: Silky or pearly luster

Identified March 22, 2026More mineral →

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Physical properties

Formation & geological history

Formed as an evaporite mineral in sedimentary environments, often resulting from the evaporation of seawater in massive basins or as a secondary mineral in veins from hydrothermal fluids. This specimen is typically found in sedimentary rock layers spanning multiple geological ages.

Uses & applications

Commonly used in the production of plaster of Paris, wallboard (drywall), and as a soil conditioner. In its fibrous 'Satin Spar' form, it is highly popular for metaphysical collecting, decorative carvings, and ornamental wands.

Geological facts

While often marketed as 'Selenite,' true Selenite is the clear, transparent variety of gypsum. Satin Spar is the opaque, fibrous variety that creates a 'cat's eye' chatoyancy effect when light reflects off its internal fibers. It is one of the softest minerals used in decorative arts.

Field identification & locations

Identify in the field by its extreme softness (can be scratched by a fingernail) and fibrous texture. Common locations include Morocco, Mexico, USA (Utah/New Mexico), and Italy. Collectors should avoid getting it wet as it can slowly dissolve or lose its luster in water.

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