metamorphic
Quartzite
Quartzite
Hardness: 7 on Mohs scale; Color: typically white, gray, or tan (this specimen is tan/yellow-tinted); Luster: vitreous or dull; Structure: non-foliated, granular texture; Cleavage: none, breaks with conchoidal or irregular fracture.
- Hardness
- 7 on Mohs scale
- Luster
- vitreous or dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or tan (this specimen is tan/yellow-tinted); Luster: vitreous or dull; Structure: non-foliated, granular texture; Cleavage: none, breaks with conchoidal or irregular fracture.
Formation & geological history
Formed through the metamorphism of quartz sandstone. Under high heat and pressure, the individual quartz grains recrystallize and fuse together, creating a dense, interlocking matrix. This process occurs during mountain-building events.
Uses & applications
Used in construction as crushed stone for road grit and railway ballast, as a decorative building stone for countertops and flooring, and occasionally in glassmaking if the silica content is exceptionally high.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock during weathering, forming the peaks of many resistant mountain ridges. It is often confused with marble, but can be distinguished because quartzite will scratch glass and does not fizz in acid.
Field identification & locations
Identify in the field by its sugary, granular texture and extreme hardness. It won't be scratched by a steel knife. Common worldwide in ancient mountain ranges such as the Appalachians and the Alps.
