mineral

Satin Spar (often marketed as Selenite)

Fibrous Gypsum (CaSO4·2H2O)

Hardness: 2.0 on Mohs scale (can be scratched by a fingernail). Color: White, pearly, or translucent. Luster: Silky or pearly. Crystal Structure: Monoclinic; occurs in fibrous, parallel bundles. Cleavage: Perfect in one direction. Specific Gravity: 2.3.

Hardness: 2
Color: White, pearly, or translucent
Luster: Silky or pearly

Identified March 15, 2026More mineral →

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Physical properties

Formation & geological history

Formed as an evaporite mineral in sedimentary environments, specifically in ancient sea beds or salt lakes. It can also form through the oxidation of sulfide ores or around volcanic vents. Age varies globally from Precambrian to modern formations.

Uses & applications

Used in the manufacturing of dry wall (plasterboard), plaster of Paris, and soil conditioners. In the metaphysical and collecting market, it is popular for 'cleansing' wands, lamps, and decorative carvings.

Geological facts

While often sold as 'Selenite', true Selenite is the clear, transparent variety of gypsum. This fibrous variety is 'Satin Spar'. It is so soft that it is water-soluble over long periods of time; immersing it in water will eventually dissolve or dull the specimen.

Field identification & locations

Identify in the field by its extreme softness (scratches with a fingernail) and fibrous 'cat's eye' silky luster. It is commonly found in Morocco, Mexico (Naica Mine), and the USA (Utah and New Mexico). Collectors should avoid getting it wet and handle with care as it splinters easily into needle-like shards.

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