metamorphic
Quartzite Cobble
Metamorphic Quartz-rich Rock (SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or tan; Luster: dull to vitreous; Structure: non-foliated, granular; Cleavage: none (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Color
- typically white, gray, or tan
- Luster
- dull to vitreous
Identified More metamorphic →
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; Luster: dull to vitreous; Structure: non-foliated, granular; Cleavage: none (conchoidal fracture).
Formation & geological history
Formed from the metamorphism of quartz sandstone under high heat and pressure, causing the original quartz grains to recrystallize and fuse together. Often found as rounded river cobbles due to water erosion.
Uses & applications
Used in construction as crushed stone or road ballast, as a decorative stone in landscaping, and historically for stone tools due to its hardness.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, remaining as rounded stones in stream beds or high ridges on mountains.
Field identification & locations
Identify by its extreme hardness (will scratch glass easily) and its sugary, granular surface that looks like sand but cannot be rubbed off. Common in river beds and glacial till.
More like this
