Satin Spar Selenite
Gypsum var. Satin Spar · Decorative Stone and Mineral Specimen
Crystal System
Monoclinic; typically forms in fibrous, columnar, or satin-like masses, as well as tabular crystals.
Mineral Group
Sulfates; specific subgrouping includes hydrated calcium sulfates.
Chemical Formula
CaSO4 · 2H2O
Formation Process
Sedimentary formation through the evaporation of sulfate-rich water in restricted marine basins or desert lakes, occasionally hydrothermal or weathering processes.
About This Crystal
The specimen is a tumbled or slightly shaped cylinder of fibrous white gypsum, commonly known as satin spar. It exhibits a translucent to opaque appearance with a distinct silky luster characteristic of fibrous crystal growth.
Physical Characteristics
Color is white to off-white with a white streak. It has perfect cleavage in one direction, producing flexible flakes, and an uneven or fibrous fracture. Specific gravity is approximately 2.30. Tenacity is sectile and flexible.
Optical Properties
Biaxial positive with refractive indices around 1.520 to 1.530. Displays a strong chatoyant effect (cat's-eye) due to the fibrous parallel structure when polished into curved or cylindrical shapes.
Hardness & Durability
Origin Region
Notable sources include Mexico, Morocco, Poland, and the USA. It typically forms in evaporite sedimentary environments and saline lakes.
Hardness & Durability
Mohs hardness of 2, making it very soft and easily scratched by a fingernail. Low durability and poor wearability for everyday jewelry.
Care & Maintenance
Extremely water-soluble; must never be cleaned with water or soaked. Clean only with a dry cloth. Store separately to avoid scratching, away from high humidity.
Rarity & Value
Common and widely available. Inexpensive as tumbled stones, polished shapes, or decorative carvings. Treatments are rare as the material is abundant.
Special Characteristics
Pronounced silky chatoyancy (satin-like sheen) due to the micro-fibrous structure reflecting light along parallel channels.
Lore & History
Named after the Greek word 'selene' meaning moon due to its moon-like glow. In crystal healing lore, it is traditionally associated with the crown chakra, clearing negative energy, and promoting mental clarity, though these are traditional cultural beliefs rather than scientifically verified claims.