metamorphic
Quartzite
Metamorphic Quartzite (primarily SiO2)
Hardness: 7 on the Mohs scale, Color: White, gray, pink, brown, or reddish, Luster: Vitreous to greasy, Crystal structure: Interlocking quartz crystals (non-foliated), Cleavage: None (fractures conchoidally), Specific gravity: 2.65
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Physical properties
Hardness: 7 on the Mohs scale, Color: White, gray, pink, brown, or reddish, Luster: Vitreous to greasy, Crystal structure: Interlocking quartz crystals (non-foliated), Cleavage: None (fractures conchoidally), Specific gravity: 2.65
Formation & geological history
Formed from quartz-rich sandstone or chert under high temperature and pressure associated with regional metamorphism. Geological age varies widely depending on the formation region, ranging from Precambrian to Cenozoic.
Uses & applications
Used in construction, railroad ballast, crushed stone for road construction, manufacture of silica brick, and occasionally as an ornamental stone or for countertops.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why quartz-rich mountain ridges often remain as prominent ridges or peaks after surrounding softer rock has eroded.
Field identification & locations
Identified in the field by its sugary texture on fractured surfaces, extreme hardness (scratches glass easily), and lack of fizz when tested with hydrochloric acid (distinguishing it from marble). Found worldwide.
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