Cryolite is a rare sodium aluminum fluoride most famous for its primary historic occurrence in Ivigtut, Greenland, where it formed a massive deposit. It is notable for having a refractive index very close to that of water, making it appear to disappear when immersed in a glass of water. It typically occurs as massive, white to colorless granular masses rather than well-defined crystals.
Is this cryolite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch cryolite with a known reference. Cryolite sits at Mohs 2.5-3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Cryolite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Cryolite typically shows a vitreous to greasy luster.
- 4Match the color rangeCompare against the expected color range: white, colorless, yellowish, reddish, brownish.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: pseudocubic crystals, massive, granular.
Often confused with
Cryolite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Quartz is the harder of the two (Mohs 7 vs. 2.5-3); luster reads vitreous to greasy on Cryolite and vitreous on Quartz.
How to tell apart: Fluorite is the harder of the two (Mohs 4 vs. 2.5-3); luster reads vitreous to greasy on Cryolite and vitreous on Fluorite.
How to tell apart: Albite is the harder of the two (Mohs 6-6.5 vs. 2.5-3); luster reads vitreous to greasy on Cryolite and vitreous on Albite.
Often found alongside cryolite
Minerals reported to co-occur with cryolite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₃AlF₆
- Mohs hardness
- 2.5-3
- Density
- 2.95-3.0 g/cm³
- Streak
- White
- Luster
- Vitreous to Greasy
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Pseudocubic Crystals, Massive, Granular
- Cleavage
- Poor in Three Directions
- Rarity
- Rare
- Uses
- Collector, Industrial (formerly For Aluminum Smelting)
- Host rock
- Granite Pegmatites
- Typical price
- $20-200 thumbnail, $300+ cabinet specimen
Where rockhounds find cryolite
Classic worldwide localities
- Ivigtut, Greenland
- Pikes Peak, Colorado, USA
- Miass, Ural Mountains, Russia
- Mont Saint-Hilaire, Quebec, Canada
Field-hunting tip
Look in granite pegmatites country, the host setting where cryolite typically forms. If you start seeing siderite, galena, chalcopyrite in float, you are in the right ground. Field specimens usually show a pseudocubic crystals, massive, granular habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find cryolite on the map
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