metamorphic
Quartzite
Quartzite (Metamorphosed Quartz Sandstone)
Hardness: 7 on the Mohs scale, Color: Pink, reddish-brown, white, or gray, Luster: Vitreous to greasy on fresh surfaces, sugary texture, 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: Pink, reddish-brown, white, or gray, Luster: Vitreous to greasy on fresh surfaces, sugary texture, Crystal structure: Interlocking quartz crystals (non-foliated), Cleavage: None (fractures conchoidally), Specific gravity: 2.65
Formation & geological history
Formed when quartz-rich sandstone is subjected to high heat and pressure, typically through tectonic compression in orogenic belts. Geological age varies widely from Precambrian to Cenozoic.
Uses & applications
Used in construction, as crushed stone for roadbeds, railway ballast, dimension stone, and manufacturing silicon and ferrosilicon.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why ridges formed of quartzite often persist as prominent hills or mountain crests.
Field identification & locations
Identify by its hardness (scratches glass easily, cannot be scratched by a steel knife) and the visible or microscopic interlocking quartz grains. Commonly found in mountainous regions and ancient cratons worldwide.
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