Cryolite
Cut cryolite is somewhat translucent, and has a “sleepy” look. The cuttable material has a very low birefringence, is colorless, and very soft—not exactly an exciting-looking gem. However, there are very few cut stones in existence because of the extreme scarcity of suitable rough. In addition, cryolite is only found abundantly at one locality (Ivigtut).
Optics: a = 1.338; β = 1.338; γ = 1.339.
Biaxial (+), 2V= 43°.
Occurrence: Occurs in alkalic rocks at Ivigtut, Greenland.
Also Spain; USSR; Colorado (small amounts).
Comments: Cut cryolite is somewhat translucent, and has a “sleepy” look. The cuttable material has a very low birefringence, is colorless, and very soft—not exactly an exciting-looking gem. However, there are very few cut stones in existence because of the extreme scarcity of suitable rough. In addition, cryolite is only found abundantly at one locality (Ivigtut).
Name: From the Greek kryos (frost) and lithos (stone), hence ice-stone, in allusion to its appearance.