metamorphic
Quartzite
Quartzite (composed primarily of SiO2)
Hardness: 7 on Mohs scale; Color: Grayish-white with translucent areas; 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
- Grayish-white with translucent areas
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-white with translucent areas; 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 metamorphism of quartz-rich sandstone. High heat and pressure cause the sand grains to recrystallize and fuse together into a dense, hard rock.
Uses & applications
Used as crushed stone in construction, road ballast, and as a decorative stone in architecture and landscaping. High-purity quartzite is used in glassmaking and electronics.
Geological facts
Quartzite is so hard that it will scratch glass and steel. It is much harder and more durable than the sandstone it originated from, making it highly resistant to chemical weathering.
Field identification & locations
Identify in the field by its extreme hardness and the fact that it breaks across grain boundaries rather than around them. It is commonly found in folded mountain belts and ancient cratons worldwide.
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