metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or tan; Luster: vitrous to dull; Crystal structure: hexagonal (trigonal); Grain: fine to medium grained with a sugary texture.
- Hardness
- 7 on Mohs scale
- Color
- typically white, gray, or tan
- Luster
- vitrous 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: typically white, gray, or tan; Luster: vitrous to dull; Crystal structure: hexagonal (trigonal); Grain: fine to medium grained with a sugary texture.
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone under intense heat and pressure, causing the original quartz grains to recrystallize and fuse together.
Uses & applications
Used in construction as road ballast, gravel, and dimension stone; also used for decorative purposes, landscaping, and as a raw material for glass manufacturing.
Geological facts
Quartzite is so tough that it often breaks through the individual quartz grains rather than around them, which distinguishes it from sandstone. Some varieties can be billions of years old.
Field identification & locations
Identify by its extreme hardness (it will scratch glass) and lack of reaction to acid. Look for it in mountainous regions or as rounded cobbles in riverbeds and glacial deposits.
