metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or tan (iron can tint it pink or reddish); Luster: vitreous to dull; Crystal structure: hexagonal (microcrystalline); Cleavage: none, breaks with a conchoidal fracture.
- Hardness
- 7 on Mohs scale
- Luster
- vitreous to dull
Identified More metamorphic →
Explore Quartzite in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or tan (iron can tint it pink or reddish); Luster: vitreous to dull; Crystal structure: hexagonal (microcrystalline); Cleavage: none, breaks with a conchoidal fracture.
Formation & geological history
Formed from the metamorphism of quartz sandstone. High pressure and heat cause the sand grains to recrystallize and fuse together, creating a hard, dense rock.
Uses & applications
Used in construction as crushed stone for road beds, as dimension stone for counter tops and flooring, and occasionally in glassmaking if pure enough.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks in a landscape, forming prominent ridges and hills. It is harder than steel and will easily scratch a glass plate.
Field identification & locations
Identify it by its glassy appearance on fresh breaks and its extreme hardness. It won't react with acid (unlike marble). Commonly found in mountain ranges and ancient shield areas globally.
