metamorphic
Quartzite
Quartzite (primarily Silicon Dioxide, SiO2)
Hardness: 7 (Mohs scale), Color: White to grey (sometimes pink or yellow), Luster: Vitreous to dull, Crystal structure: Trigonal (hexagonal in appearance), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6 - 2.8
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Physical properties
Hardness: 7 (Mohs scale), Color: White to grey (sometimes pink or yellow), Luster: Vitreous to dull, Crystal structure: Trigonal (hexagonal in appearance), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6 - 2.8
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. Under intense heat and pressure, grain boundaries fuse together into a dense, crystalline mass. It is found in mountain belts and Precambrian shield areas worldwide.
Uses & applications
Used in construction as crushed stone for road ballast, floor tiles, and decorative wall coverings. High-purity quartzite is used in the manufacture of glass and silicon metal for electronics.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock in the landscape, forming prominent ridges and hills. It is often confused with marble, but can be distinguished by its much higher hardness (it scratches glass, while marble does not).
Field identification & locations
Identify in the field by its hardness (it should easily scratch steel or glass) and its sugary, crystalline texture. It is often found in river beds as rounded white cobbles. Look for it in regions with old, folded mountain ranges.
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