metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or brown but can be reddish due to iron oxides; Luster: Vitreous to dull; Structure: Granoblastic (sugary texture); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7.
- 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 brown but can be reddish due to iron oxides; Luster: Vitreous to dull; Structure: Granoblastic (sugary texture); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7.
Formation & geological history
Formed when quartz-rich sandstone is subjected to high heat and pressure (regional or contact metamorphism), causing the quartz grains to recrystallize and fuse into a dense rock. Most deposits are Proterozoic to Paleozoic in age.
Uses & applications
Used in construction as crushed stone for road beds or railway ballast, as dimension stone for counter-tops and flooring, and sometimes as a source of silica in glassmaking.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the crests of mountain ridges through differential erosion. It is significantly harder than the sandstone it originates from.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by a steel nail) and the way it fractures across individual sand grains rather than around them. Commonly found in folded mountain belts.
More like this
