metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: White to light grey with tan staining; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- White to light grey with tan staining
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: White to light grey with tan staining; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); 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 quartz grains to recrystallize and fuse together, creating a dense, interlocking matrix.
Uses & applications
Used widely in construction as crushed stone for road ballast, flooring, roofing tiles, and as a decorative stone in landscaping or interior design (countertops).
Geological facts
Quartzite is so hard and chemically resistant that it often forms the ridges and peaks of mountain ranges because it weathers much slower than the surrounding rock.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass and steel) and its crystalline appearance. Unlike sandstone, quartzite breaks through the quartz grains rather than around them.
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