metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: tan, yellow-brown, and white with iron staining; Luster: vitreous to dull; Crystal structure: hexagonal (microcrystalline); Cleavage: none, breaks with conchoidal or irregular fracture.
- Hardness
- 7 on Mohs scale
- Color
- tan, yellow-brown, and white with iron staining
- 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: tan, yellow-brown, and white with iron staining; Luster: vitreous to dull; Crystal structure: hexagonal (microcrystalline); Cleavage: none, breaks with conchoidal or irregular fracture.
Formation & geological history
Formed when quartz-rich sandstone is subjected to high heat and pressure, causing the quartz grains to recrystallize and fuse into a dense, indestructible rock. This specimen appears water-worn, likely from a river or glacial deposit.
Uses & applications
Used extensively in road construction (crushed stone), as railway ballast, and occasionally for high-end countertops or architectural stone. This specific piece is a common field stone.
Geological facts
Quartzite is so tough that it often survives intense erosion and transport over hundreds of miles, outlasting the softer rocks that originally surrounded it. It is often harder than the steel blade of a knife.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel blade) and granular texture that looks like sand but does not rub off. Found in mountain ranges and glacial till globally.
More like this
