mineral

Satin Spar (often marketed as Selenite)

Fibrous Gypsum (CaSO4·2H2O)

Hardness: 2 on Mohs scale (can be scratched by a fingernail). Color: Pearly white to translucent. Luster: Silky/Satin. Crystal structure: Monoclinic, typically found in fibrous, parallel growth. Cleavage: Perfect in one direction, though appearance is dominated by the fibrous structure.

Hardness: 2 on Mohs scale (can be scratched by a fingernail)
Color: Pearly white to translucent
Luster: Silky/Satin

Identified March 23, 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 beds. It can also form through the hydration of anhydrite or the oxidation of sulfides.

Uses & applications

Commonly used in plaster and drywall (as gypsum), as a soil conditioner, and in the metaphysical/crystal collecting market for carved lamps, charging plates, and decorative wands.

Geological facts

While commonly called 'Selenite' in the trade, true Selenite is the clear, tabular variety of gypsum. This fibrous variety is technically Satin Spar. It is named for its silky appearance which catches light in a way similar to satin fabric.

Field identification & locations

Identify in the field by its extreme softness and silky, fibrous appearance. It is very common in Morocco, Mexico, and parts of the United States (Utah). Collectors should note it is water-soluble over long periods and very fragile.

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