From The Gemology Project
Jump to: navigation, search
Chemical composition Cesium Beryllium Lithium Aluminium Silicate Cs(Be2Li)Al2Si6O18
Crystal system Trigonal
Habit subhedral-to-euhedral hexagonal tabular
Cleavage imperfect (basal)
Fracture conchoidal to irregular
Hardness 8
Optic nature uniaxial -
Refractive index 1.601-1.620
Birefringence 0.011
Dispersion unknown
Specific gravity 3.04-3.14
Lustre vitreous
Pleochroism moderate to strong