metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: white to pale yellow/tan with sugary texture; 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 pale yellow/tan with sugary texture
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: white to pale yellow/tan with sugary texture; 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. Heat and pressure cause the original quartz grains to recrystallize and fuse together into a dense, hard rock.
Uses & applications
Used in construction as road ballast, gravel, and building stone. High-purity quartzite is used to produce silica sand for glassmaking and industrial abrasives.
Geological facts
Quartzite is so hard and resistant to chemical weathering that it often forms the crests of ridges and resistant hilltops. It is frequently confused with white marble, but unlike marble, it will not fizz with acid and can scratch glass.
Field identification & locations
Identify by its 'sugary' interlocking crystalline texture and extreme hardness. It won't be scratched by a steel knife. Commonly found in ancient mountain belts and as river-worn cobbles.
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