RocksdayCryolite vs Quartz
The quickest way to tell Cryolite from Quartz: Quartz scratches glass (Mohs 7); Cryolite can't (Mohs 2.5).
A rare sodium-aluminum fluoride. The only large deposit, at Ivittuut in Greenland, was mined until 1987 as the flux that made aluminum smelting practical.
Photo: Didier Descouens, CC BY-SA 3.0
The second most abundant mineral in Earth's crust. Clear crystals grow as six-sided prisms capped by a pointed termination, and quartz shows up as grains in sand, granite and countless other rocks.
Photo: Didier Descouens, CC BY-SA 4.0
Quick tests
- Scratch glass: Quartz scratches glass (Mohs 7); Cryolite can't (Mohs 2.5).
Key differences
- Quartz is much harder.
Side by side
| Property | Cryolite | Quartz |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 2.5 | 7 |
| Luster | Vitreous to greasy | Vitreous |
| Streak | White | White |
| Colors | White, Clear, Gray | Clear, White, Gray |
| Crystal system | Monoclinic | Trigonal |
| Specific gravity | 2.95–3 | 2.65 |
| Formula | Na₃AlF₆ | SiO₂ |
| Found in | Ivittuut, Greenland | Hot Springs, Arkansas; Minas Gerais, Brazil |
Properties that are the same for both are grayed out.
How to identify cryolite
- Colorless to white, waxy masses.
- A fingernail barely scratches it.
- Powdered in water, it nearly disappears — its refractive index is close to water's.
Crystal system: Monoclinic
Full Cryolite guide →How to identify quartz
- Scratches glass easily and can't be scratched by a steel knife.
- Six-sided prisms with pointed ends when it forms crystals.
- Breaks with curved, shell-like (conchoidal) fractures — no flat cleavage planes.
- Does not fizz in vinegar or dilute acid.
Crystal system: Trigonal
Full Quartz guide →More comparisons
Frequently asked questions
What is the difference between cryolite and quartz?
Cryolite is a mineral (Na₃AlF₆) with a Mohs hardness of 2.5 and a vitreous to greasy luster, usually white, colorless or gray. Quartz is a mineral (SiO₂) with a Mohs hardness of 7 and a vitreous luster, usually colorless, white or gray.
How can you tell cryolite from quartz?
Quartz scratches glass (Mohs 7); Cryolite can't (Mohs 2.5). Quartz is much harder.
Could you tell them apart from a blurry close-up?
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