Rob Lavinsky, iRocks.com – CC-BY-SA-3.0 [CC-BY-SA-3.0], via Wikimedia Commons
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).
Cryolite Value
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Cryolite Information
| Data | Value |
| Name | Cryolite |
| Crystallography | Monoclinic. Crystals cuboidal and prismatic; usually massive. |
| Colors | Colorless, white, brownish, reddish; rarely gray to black. |
| Luster | Vitreous to greasy. |
| Hardness | 2.5 |
| Density | 2.97 |
| Birefringence | 0.001; almost isotropic. |
| Cleavage | None. Fracture uneven. Brittle. |
| Dispersion | 0.024 (approximately) |
| Stone Sizes | Large cabochons could be cut from the abundant material in Greenland. Facetable material is quite rare, however, and only tiny gems can be obtained. |
| Luminescence | None observed |
| Spectral | Not diagnostic |
| Formula | Na3AlF6. |
| Pleochroism | None |
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.
