metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 (Mohs scale); Color: White, gray, or yellowish; Luster: Vitreous to dull; Crystal structure: Trigonal (granular); Cleavage: None; Specific gravity: 2.6–2.7
- Hardness
- 7 (Mohs scale)
- Color
- White, gray, or yellowish
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: White, gray, or yellowish; Luster: Vitreous to dull; Crystal structure: Trigonal (granular); Cleavage: None; Specific gravity: 2.6–2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under extreme heat and pressure, typically during tectonic plate collisions and mountain-building events.
Uses & applications
Used in construction as crushed stone or dimension stone, in manufacturing as a source of silica, and as a durable material for countertops and flooring.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock in weathering processes, frequently forming the peaks of ridges and mountains.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by steel) and lack of reaction to acid. It is commonly found in metamorphic terranes like the Appalachian Mountains or the Alps.
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