metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale, color ranges from white and grey to pink, red, or purple due to iron oxides, vitreous to greasy luster, non-foliated massive crystal structure, poor cleavage (fractures across quartz grains rather than around them), specific gravity of 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, color ranges from white and grey to pink, red, or purple due to iron oxides, vitreous to greasy luster, non-foliated massive crystal structure, poor cleavage (fractures across quartz grains rather than around them), specific gravity of 2.65.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone or chert under high temperature and tectonic pressure, commonly developing during mountain-building events over millions of years.
Uses & applications
Used in construction as crushed stone for road bases, railway ballast, building facades, decorative landscaping, and occasionally for manufactured items like countertops and tiles.
Geological facts
Unlike sandstone, which breaks around the individual grains of sand, quartzite breaks right through them because the quartz grains recrystallize and interlock tightly during metamorphism, making it exceptionally durable.
Field identification & locations
Can be identified in the field by its extreme hardness (will easily scratch glass and cannot be scratched by a steel knife) and the characteristic sugary, sparkling texture of broken quartz crystals on fresh surfaces. Found globally in ancient mountain belts.
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