Rectangular step-cut chiolite, 1.04 cts, 6.9 x 5.6 mm, Ivigtut, Greenland. © The Gem Trader. Used with permission.
Chiolite makes a challenging gem. It’s difficult to cut, extremely rare, and has little appeal. It’s solely a curiosity in the gem world.
| Data | Value |
|---|---|
| Name | Chiolite |
| Formula | Na5Al3F14 |
| Etymology | From the Ancient Greek words khion for “snow” and lithos for “stone,” due to its white appearance. |
| Occurrence | In cryolite pegmatite. |
| Colors | Colorless, white. |
| Hardness | 3.5-4 |
| Cleavage | Perfect 1 direction |
| Crystallography | Tetragonal; minute dipyramidal crystals, commonly in masses. |
| Refractive Index | 1.342-1.349 |
| Birefringence | 0.007 |
| Luminescence | None |
| Luminescence Present | No |
| Absorption Spectrum | Not diagnostic |
| Pleochroism | None |
| Optics | o = 1.349; e = 1.342. Uniaxial ( - ). |
| Optic Sign | Uniaxial - |
| Luster | Vitreous |
| Specific Gravity | 2.998 |
| Transparency | Transparent to translucent |
Chiolite: Greenland (1.1). Photo © Joel E. Arem, PhD, FGA. Used with permission.
Less than two dozen or so cut chiolites may exist. This gem combines a very low hardness (3.5-4) and perfect cleavage with a lack of appealing colors. The stones are usually small and nondescript. However, chiolite has joined the ranks of minerals cut by faceters who must try their hand at everything clean enough to cut. Thus, a cut stone would make quite a specimen for a gem collection.
This nondescript gem also has a very similar name to cryolite, a similar, related mineral. Cryolite means “ice stone,” while chiolite means “snow stone.” Like their namesakes, they’re sometimes found together. However, chiolites are rarer.
No known synthetics or treatments.
The mineral itself is quite rare. Ivigtut, Greenland, is the principal source of gem-quality material, where it occurs in association with cryolite. Other gem-quality sources include Miask, in the Urals region of Russia, where it’s found in a cryolite pegmatite.
Chiolite specimen from Miask, Ural, Russia, on display at the Mineralogical Museum, Bonn, Germany. Photo by Ra’ike. Licensed under CC By-SA 3.0.
Always tiny, 1-2 carat range, if clean. Large, clean fragments for cutting do not exist.
A knife could scratch this stone. Store any chiolites separately from other more common, harder jewelry stones, such as quartz or topaz. See our Gemstone Jewelry Cleaning Guide for care recommendations.
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