metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 (Mohs scale); Color: Pink to reddish-orange (due to iron oxide stains); Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.65
- Hardness
- 7 (Mohs scale)
- Color
- Pink to reddish-orange (due to iron oxide stains)
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Pink to reddish-orange (due to iron oxide stains); Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.65
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause the sand grains to recrystallize and fuse together into a dense, hard mass. Often associated with mountain-building (orogenic) events.
Uses & applications
Used in construction as road ballast, gravel for railway beds, flooring, wall coverings, and decorative landscaping stone. High-purity quartzite is used in the glass and metallurgy industry.
Geological facts
Quartzite is so hard and tough that it often survives erosion better than other rocks, frequently capping hills and mountain ridges. The pink variety is often referred to as 'Pink Quartzite' or 'Sioux Quartzite' in some North American regions.
Field identification & locations
Identify by its ability to scratch glass easily and its sugary, crystalline texture that breaks through the grains rather than around them (unlike sandstone). Commonly found in Precambrian shields and fold mountain belts.
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