RocksdayMilky Quartz vs Quartz
To tell Milky Quartz from Quartz: Rock crystal is transparent; milky quartz is cloudy white.
The common white quartz. The cloudiness is light scattering off microscopic fluid bubbles trapped as the crystal grew.
Photo: James St. John, CC BY 2.0
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
Key differences
- Rock crystal is transparent; milky quartz is cloudy white.
Side by side
| Property | Milky Quartz | Quartz |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 7 | 7 |
| Luster | Vitreous to greasy | Vitreous |
| Streak | White | White |
| Colors | White | Clear, White, Gray |
| Crystal system | Trigonal | Trigonal |
| Specific gravity | 2.65 | 2.65 |
| Formula | SiO₂ | SiO₂ |
| Found in | Arkansas; Minas Gerais, Brazil | Hot Springs, Arkansas; Minas Gerais, Brazil |
Properties that are the same for both are grayed out.
How to identify milky quartz
- White and translucent rather than glassy-clear.
- Hardness 7 — scratches glass, no cleavage.
- Often massive veins or chunky crystals.
Crystal system: Trigonal
Full Milky Quartz 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 milky quartz and quartz?
Milky Quartz is a mineral (SiO₂) with a Mohs hardness of 7 and a vitreous to greasy luster, usually white. Quartz is a mineral (SiO₂) with a Mohs hardness of 7 and a vitreous luster, usually colorless, white or gray.
How can you tell milky quartz from quartz?
Rock crystal is transparent; milky quartz is cloudy white.
Could you tell them apart from a blurry close-up?
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