metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or tan but can be reddish due to iron oxides; Luster: vitreous to dull; Crystal structure: non-foliated, interlocking quartz grains; Cleavage: none.
- Hardness
- 7 on Mohs scale
- Luster
- vitreous to dull
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 but can be reddish due to iron oxides; Luster: vitreous to dull; Crystal structure: non-foliated, interlocking quartz grains; Cleavage: none.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events. The individual quartz grains recrystallize into a dense, interlocking mosaic.
Uses & applications
Used widely in construction as crushed stone for road grit and railroad ballast. It is also used in the glass and chemical industries due to its high silica content, and as a decorative stone in architecture.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, frequently forming the caps of ridges and mountains. It is also more resistant to chemical weathering than most other rocks.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass) and lack of foliation. Unlike sandstone, when broken, quartzite breaks across the grain rather than around the individual sand grains. Often found in glaciated regions as erratic cobbles.
More like this
