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 — that is 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
How do you identify cryolite?+
Where is cryolite found?+
How much is cryolite worth?+
What rocks look like cryolite?+
What minerals are found with cryolite?+
What kind of rock does cryolite form in?+
What is cryolite used for?+
Find cryolite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
