metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or reddish due to iron oxidation; Luster: vitreous to waxy; Crystal structure: hexagonal (microcrystalline); Cleavage: none; Specific gravity: 2.6–2.7
- Hardness
- 7 on Mohs scale
- Color
- typically white, gray, or reddish due to iron oxidation
- Luster
- vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or reddish due to iron oxidation; Luster: vitreous to waxy; Crystal structure: hexagonal (microcrystalline); Cleavage: none; Specific gravity: 2.6–2.7
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. High heat and pressure cause the sand grains to recrystallize and fuse together, typically in orogenic (mountain-building) belts.
Uses & applications
Used as crushed stone for road construction, railway ballast, and as a raw material for glass and ceramic manufacturing. High-quality slabs are used for countertops and flooring.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the tops of ridges and resistant hills because it weathers much more slowly than the surrounding rock.
Field identification & locations
Identify it by its ability to scratch glass and the way it breaks through sand grains rather than around them (unlike sandstone). Commonly found in the Appalachian Mountains, Lake Superior region, and Brazil.
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