metamorphic
Quartzite
Quartzite (mostly SiO2)
Hardness: 7 on Mohs scale; Color: tan, white, or gray; Luster: vitreous to dull; Crystal structure: trigonal (granular); Cleavage: none (conchoidal fracture); Specific gravity: 2.63-2.65
- Hardness
- 7 on Mohs scale
- Color
- tan, white, or gray
- Luster
- vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: tan, white, or gray; Luster: vitreous to dull; Crystal structure: trigonal (granular); Cleavage: none (conchoidal fracture); Specific gravity: 2.63-2.65
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure, causing the original quartz grains to recrystallize into an interlocking mosaic.
Uses & applications
Used in construction for road ballast, flooring, and wall facings; also used in glass manufacturing and as a decorative architectural stone.
Geological facts
Quartzite is so tough that it can scratch steel and is more resistant to chemical weathering than most other rocks. It often outlasts mountains and forms prominent ridges.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel knife) and its grainy, sugary texture. It is commonly found in fold mountain belts globally.
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