Rock Identifier
Satin Spar (often marketed as Selenite) (Gypsum (Calcium Sulfate Dihydrate) - CaSO4·2H2O) — mineral
mineral

Satin Spar (often marketed as Selenite)

Gypsum (Calcium Sulfate Dihydrate) - CaSO4·2H2O

Hardness: 2 on Mohs scale (can be scratched by a fingernail). Color: White or pearly white. Luster: Pearly to silky (satin-like). Crystal structure: Monoclinic, often fibrous. Cleavage: Perfect one-way cleavage. Specific Gravity: 2.3.

Hardness
2 on Mohs scale (can be scratched by a fingernail)
Color
White or pearly white
Luster
Pearly to silky (satin-like)
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Physical properties

Hardness: 2 on Mohs scale (can be scratched by a fingernail). Color: White or pearly white. Luster: Pearly to silky (satin-like). Crystal structure: Monoclinic, often fibrous. Cleavage: Perfect one-way cleavage. Specific Gravity: 2.3.

Formation & geological history

Formed as an evaporite mineral in sedimentary environments, such as ancient seabeds and salt flats where mineral-rich water evaporates. It can form in various geological ages where saline lakes or marine basins were present.

Uses & applications

Primarily used in the metaphysical and spiritual industry for 'cleansing' other stones. Gypsum is used industrially in drywall (plasterboard), cement, and as a soil conditioner (land plaster).

Geological facts

While commonly sold as 'Selenite,' this fibrous white variety is technically 'Satin Spar.' True Selenite is transparent and forms flat, window-like plates. This specimen is shaped into a 'skyscraper' or 'tower' form, which is a popular decorative cut.

Field identification & locations

Identify in the field by its extreme softness (scratches with a nail) and its fibrous, silky luster. Commonly found in Morocco, Mexico, and the USA (Utah/New Mexico). Note: It is water-soluble over time and should not be soaked.

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