Chiolite: Gemstones Information

Chiolite is Na5Al3F14 and forms very small dipyramidal crystals of the tetragonal system and, more commonly, transparent to translucent near colourless to snow-white masses with a perfect cleavage in one direction,hardness 3.5–4 and SG 2.90. The RI for the ordinary and extraordinary rays is 1.349 and 1.342, uniaxial negative with birefringence 0.007.Chiolite occurs in some granite pegmatites; any fashioned specimens are most likely to have come from the Ivigtut cryolite deposit, south-west Greenland.