Afghanite
A variety of Cancrinite Group
What is Afghanite?
The remarkable blue appearance of afghanite is a very recent discovery, dating back to just 1968. It is incredibly rare! Since its initial discovery, it has only been found in Afghanistan and a few minuscule bands elsewhere. It is an incredibly complex crystal comprised of eleven different elements.
Etymology & Origins
It was discovered in 1968 in the Lapis-lazuli Mine, Sar-e-Sang, Badakhshan Province, Afghanistan and takes its name from that country.
Uses & Applications
It is used as a gemstone.
Optical Properties
- Refractive Index
- 1.522-1.533
- Birefringence
- 0.006
- Optical Character
- Biaxial positive
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Key Characteristics
Characteristics of Afghanite
Afghanite is a feldspathoid of the cancrinite group and typically occurs with sodalite group minerals. It forms blue to colorless, typically massive crystals in the trigonal crystal system. The lowering of the symmetry from typical (for cancrinite group) hexagonal one is due to ordering of Si and Al. It has a Mohs hardness of 5.5 to 6 and a specific gravity of 2.55 to 2.65. It has refractive index values of nω=1.523 and nε=1.529. It has one direction of perfect cleavage and exhibits conchoidal fracture. It fluoresces a bright orange.
Formation of Afghanite
It occurs as veinlets in lazurite crystals in the Afghan location and in altered limestone xenoliths within pumice in Pitigliano, Tuscany, Italy.
Composition of Afghanite
Afghanite is a hydrous sodium, calcium, potassium, sulfate, chloride, carbonate alumino-silicate mineral.
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Quick Facts
Physical Properties
- Color
- white, light blue, dark blue
- Hardness (Mohs)
- 5.5 - 6
- Density
- 2.65 g/cm³
- Streak
- white
- Luster
- Vitreous
- Crystal System
- Trigonal
Chemical Properties
- Chemical Formula
- (Na,K)22Ca10(Si24Al24O96)(SO4)6Cl6
- Elements
- Al, Ca, Cl, K, Na, O, S, Si
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