metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Pink, reddish-brown, tan, or white; Luster: Vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: None (conchoidal to uneven fracture); Specific gravity: 2.63–2.65
- Hardness
- 7 on Mohs scale
- Color
- Pink, reddish-brown, tan, or white
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Pink, reddish-brown, tan, or white; Luster: Vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: None (conchoidal to uneven fracture); Specific gravity: 2.63–2.65
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause the quartz grains to recrystallize and fuse together, creating a dense, hard rock.
Uses & applications
Used in construction as crushed stone for road beds or railway ballast, as a decorative building stone (facades and flooring), and in glass manufacturing if the silica content is high enough.
Geological facts
Quartzite is so tough that it often outlasts other rocks in the field, forming prominent ridges and hills. Unlike sandstone, quartzite breaks through its individual grains rather than around them.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel knife) and its grainy, crystalline texture. It is commonly found in mountain ranges and ancient metamorphic shields globally.
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