metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: White, gray, or yellowish; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline masses); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6 - 2.7
- Hardness
- 7 on Mohs scale
- Color
- White, gray, or yellowish
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: White, gray, or yellowish; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline masses); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6 - 2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during regional mountain-building events (orogeny).
Uses & applications
Used as crushed stone for road construction, railway ballast, and as a raw material in the glass and ceramics industries. Polished slabs are used for countertops and flooring.
Geological facts
Quartzite is so durable that it often forms the tops of ridges and mountains because it resists weathering much better than the surrounding rocks.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass) and its granular, sandpaper-like texture that lacks the distinct foliation of gneiss. It is commonly found in metamorphic terranes worldwide.
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