Afghanite
Image: Robert M. Lavinsky (CC BY-SA 3.0)
Mineral NameAfghanite
Chemical Formula(Na,K)22Ca10(Si24Al24)O96(SO4)6Cl6·H2O
Mohs Hardness5.5
Crystal Systemhexagonal
Streak ColorWhite
CleavageDistinct on {1010}
FractureConchoidal to uneven
Specific Gravity2.6
Colorsblue, light blue, dark blue, colorless, white, gray, green
TransparencyTransparent to translucent
Type LocalitySar-e-Sang District, Koksha Valley, Badakhshan Province, Afghanistan
Mineral GroupSilicates (Feldspathoid, Cancrinite group)
Usescollector, gemstone (rarely)
Associated Mineralsquartz, lazurite, pyrite, calcite, diopside
Rarityrare
Description
A prominent, elongated, deep blue Afghanite crystal or aggregate is embedded within a lighter, yellowish-brown matrix. The Afghanite exhibits a translucent quality and an irregular, somewhat fibrous or granular surface texture.
Geological Context
Afghanite typically forms in contact metamorphic or metasomatic environments, often found in metamorphosed limestones and marble deposits, particularly those associated with lazurite. Its formation is linked to high-temperature, high-pressure conditions.
