metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Reddish-pink, orange-brown, or grey; Luster: Vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: None; Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- Reddish-pink, orange-brown, or grey
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Reddish-pink, orange-brown, or grey; Luster: Vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: None; Specific gravity: 2.6-2.7.
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events. Geological age varies but often Proterozoic to Paleozoic.
Uses & applications
Used in construction as road ballast, railway ballast, and decorative stone. Sometimes used in glass making or as a source of silica in industry.
Geological facts
Quartzite is so tough that it often breaks through the quartz grains rather than around them. It is one of the most resistant rocks to chemical weathering.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by steel) and sugary, granular texture. Commonly found in folded mountain belts and glacial till.
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