metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Reddish-brown to pink (due to iron oxide); Luster: Vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: None, fractures through quartz grains; Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Reddish-brown to pink (due to iron oxide)
- Luster
- Vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: Reddish-brown to pink (due to iron oxide); Luster: Vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: None, fractures through quartz grains; Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure, typically during tectonic plate collisions and mountain-building events (orogeny).
Uses & applications
Used as decorative stone in architecture, railway ballast, road aggregate, and as a raw material for silica glass production or manufacturing silicon.
Geological facts
Unlike sandstone, which breaks around its individual grains, quartzite is so hard and compact that it breaks through the quartz grains themselves. Resistance to weathering makes it a common ridge-former in mountains.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel knife) and its sugary, crystalline texture. Commonly found in folded mountain belts globally.
