metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Pink, reddish, or tan; Luster: Vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- Pink, reddish, or tan
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Pink, reddish, or tan; Luster: Vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. Under intense heat and pressure, original quartz grains recrystallize and fuse together into a dense, crystalline rock.
Uses & applications
Used as a decorative stone in construction, railway ballast, aggregate for road building, and as a raw material for silica manufacturing. Highly valued for its durability.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the caps of mountains and ridges through differential weathering. It can be distinguished from sandstone because it breaks across grain boundaries rather than around them.
Field identification & locations
Identify in the field by its inability to be scratched by steel, its grainy yet crystalline appearance, and its tendency to break into sharp angular fragments. Commonly found in folded mountain belts.
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