metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: White to grey, sometimes reddish or brown due to iron oxides; Luster: Vitreous to dull; Structure: Granular/crystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- White to grey, sometimes reddish or brown due to iron oxides
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: White to grey, sometimes reddish or brown due to iron oxides; Luster: Vitreous to dull; Structure: Granular/crystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause the sand grains to recrystallize and fuse together. It can be found in mountain belts and areas of uplifted crust globally.
Uses & applications
Used as a decorative stone in landscaping, as crushed stone for road construction and railway ballast, and occasionally in glassmaking or as a building material for flooring and wall cladding.
Geological facts
Quartzite is so hard that it can easily scratch glass. Unlike sandstone, which breaks around the individual sand grains, quartzite breaks through the grains due to the intense fusion during metamorphism.
Field identification & locations
Identify it by its extreme hardness and its crystalline, sugary appearance. It won't fizz with acid (unlike marble). Commonly found in riverbeds as rounded cobbles or in massive outcrops in metamorphic terrains.
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