metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Reddish-brown, pink, or gray; Luster: Vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Reddish-brown, pink, or gray
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Reddish-brown, pink, or gray; Luster: Vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone under intense heat and pressure, causing recrystallization of quartz grains. Commonly Proterozoic to Paleozoic in age.
Uses & applications
Used in construction as road ballast, gravel, and dimension stone; high-purity quartzite is used to produce ferrosilicon and industrial silica.
Geological facts
Quartzite is so tough that it often survives intense weathering better than the rocks around it, frequently forming the caps of ridges and mountain peaks.
Field identification & locations
Identify by its hardness (it will easily scratch glass) and its sugary, granular texture that looks like sandstone but breaks across the grains rather than around them. Commonly found in mountain belts.
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