metamorphic
Quartzite
Quartzite (chiefly SiO2)
Hardness: 7 (Mohs scale), Color: White, gray, or reddish/brown due to iron impurities, Luster: Vitreous to dull, Structure: Granoblastic texture with fused quartz grains, Cleavage: None (conchoidal fracture)
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Physical properties
Hardness: 7 (Mohs scale), Color: White, gray, or reddish/brown due to iron impurities, Luster: Vitreous to dull, Structure: Granoblastic texture with fused quartz grains, Cleavage: None (conchoidal fracture)
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone under high heat and pressure, where individual quartz grains recrystallize and fuse together.
Uses & applications
Used in construction as road ballast, gravel, and dimension stone for flooring and walls. High-purity quartzite is used to produce silica sand for glassmaking and silicon for electronics.
Geological facts
Quartzite Is so tough that it often survives intense weathering better than other rocks, frequently forming the rugged caps of mountain ridges and peaks.
Field identification & locations
Identify by its extreme hardness (it will easily scratch glass and steel) and its crystalline, sugary appearance. Found worldwide in ancient mountain belts and shield areas.
