mineral

Satin Spar (Gypsum)

Hydrous calcium sulfate (CaSO4·2H2O)

Hardness: 2 on Mohs scale (can be scratched by a fingernail). Color: Pearly white or colorless. Luster: Silky/Satin-like. Crystal Structure: Monoclinic, typically fibrous. Cleavage: Perfect in one direction.

Hardness: 2 on Mohs scale (can be scratched by a fingernail)
Color: Pearly white or colorless
Luster: Silky/Satin-like

Identified March 11, 2026More mineral →

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Physical properties

Formation & geological history

Formed as an evaporite mineral through the evaporation of mineral-rich water in sedimentary basins or along hot springs and volcanic vents. It can form in various geological ages but is common in Permian and Triassic deposits.

Uses & applications

Used in the manufacture of wallboard (drywall), cement, and plaster of Paris. In its satin spar form, it is widely used for ornamental carvings, palm stones, and metaphysical jewelry.

Geological facts

Satin spar is often confused with Selenite (the transparent variety of gypsum) or Ulexite ('TV Stone'). It is so soft that it can be easily carved with wood-working tools.

Field identification & locations

Identify in the field by its distinctive fibrous, silky appearance and its extreme softness (scratchable with a fingernail). It is found worldwide, with major deposits in Morocco, Mexico, and the USA (Utah/New Mexico).

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