metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, gray, or white (often stained by iron); Luster: Vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: None; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Tan, gray, or white (often stained by iron)
- 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: Tan, gray, or white (often stained by iron); Luster: Vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: None; Specific gravity: 2.6-2.7
Formation & geological history
Quartzite is formed when quartz-rich sandstone is subjected to high heat and pressure during regional metamorphism. This process causes the original quartz grains to recrystallize and fuse together into a dense, hard rock.
Uses & applications
Used extensively in road construction, as railroad ballast, for floor tiles, wall coverings, and countertops. High-purity quartzite is used to produce ferrosilicon and industrial sand.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the ridges and peaks of mountain ranges because it weathers more slowly than the surrounding rock. It can scratch glass and steel easily.
Field identification & locations
Identify in the field by its extreme hardness and sugary, granular appearance on a fresh break. Unlike sandstone, quartzite breaks across the individual sand grains rather than around them. Found globally in ancient mountain belts.
More like this
