metamorphic
Quartzite
Metamorphosed Sandstone (SiO2)
Hardness: 7 (Mohs scale), Color: Pinkish-white with iron staining, Luster: Vitreous/Greasy, Crystal Structure: Trigonal (microcrystalline), Cleavage: Indistinct/Conchoidal fracture.
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Physical properties
Hardness: 7 (Mohs scale), Color: Pinkish-white with iron staining, Luster: Vitreous/Greasy, Crystal Structure: Trigonal (microcrystalline), Cleavage: Indistinct/Conchoidal fracture.
Formation & geological history
Formed when quartz-rich sandstone is subjected to high heat and pressure during regional metamorphism, causing the quartz grains to recrystallize and fuse together.
Uses & applications
Used in construction for road ballast, flooring, and wall coverings. High-purity quartzite is used to produce silica sand for glassmaking and industrial abrasives.
Geological facts
Quartzite is so tough that it often survives intense glacial movements and weathering better than the rocks surrounding it. It is often mistake for marble, but unlike marble, it will not fizz when exposed to acid.
Field identification & locations
Identify by its extreme hardness (it will easily scratch glass) and its lack of reaction to hydrochloric acid. Commonly found in mountainous regions or as river-worn cobbles.
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