mineral

Satin Spar (Selenite)

Gypsum (Calcium Sulfate Dihydrate) - CaSO4·2H2O

Hardness: 2 on Mohs scale (scratchable with a fingernail); Color: White to translucent; Luster: Pearly to silky; Crystal structure: Monoclinic with fibrous growth; Cleavage: Perfect in one direction; Specific gravity: 2.3

Hardness: 2 on Mohs scale (scratchable with a fingernail)
Color: White to translucent
Luster: Pearly to silky

Identified March 27, 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 marine basins or within clay deposits. It can form in various geological ages ranging from the Permian to the Holocene.

Uses & applications

Used in the manufacture of drywall (gypsum board), plaster of Paris, and soil conditioners. In its fibrous form (Satin Spar), it is popular in the metaphysical community for 'cleansing' and used for decorative wands, lamps, and jewelry.

Geological facts

While often marketed as 'Selenite,' true Selenite is the clear, plate-like variety of gypsum; this fibrous variety is technically 'Satin Spar.' It is water-soluble over long periods and should never be soaked in water as it will eventually dissolve or lose its luster.

Field identification & locations

Identification in the field is easy because it is soft enough to be scratched by a fingernail and has a distinct fibrous, silky sheen. Common locations include Morocco, Mexico (Naica Mine), and the United States (Utah and New Mexico). Collectors should look for chatoyancy (the 'cat's eye' effect) in the fibers.

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