metamorphic
Quartzite
Quartzite (Metamorphic Quartz Sandstone)
Hardness: 7 on the Mohs scale, Color: Typically shades of white to gray, pink, or yellowish depending on impurities, Luster: Vitreous to greasy on fresh surfaces, Crystal structure: Interlocking mosaic of quartz crystals, Cleavage: None (fractures conchoidally), Specific gravity: 2.65 to 2.70
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Physical properties
Hardness: 7 on the Mohs scale, Color: Typically shades of white to gray, pink, or yellowish depending on impurities, Luster: Vitreous to greasy on fresh surfaces, Crystal structure: Interlocking mosaic of quartz crystals, Cleavage: None (fractures conchoidally), Specific gravity: 2.65 to 2.70
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone or chert under high heat and pressure, typically in tectonic mountain-building events over millions of years.
Uses & applications
Used in construction, railroad ballast, decorative aggregates, manufacturing of silica brick, and sometimes as a dimension stone for countertops and wall tiles.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why quartz-rich sandstones often transform into exceptionally tough ridge-forming quartzites.
Field identification & locations
Can be identified in the field by its sugary texture on broken surfaces, extreme hardness (scratches glass easily and cannot be scratched by a knife), and lack of effervescence with hydrochloric acid. Found worldwide in ancient mountain belts.
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