metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale, colors range from white and gray to pink or brown depending on impurities, vitreous to greasy luster, massive crystal structure with interlocking quartz grains, conchoidal fracture, specific gravity around 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, colors range from white and gray to pink or brown depending on impurities, vitreous to greasy luster, massive crystal structure with interlocking quartz grains, conchoidal fracture, specific gravity around 2.65.
Formation & geological history
Formed from quartz-rich sandstone or chert under high temperature and pressure during regional metamorphism, often occurring in mountain-building belts.
Uses & applications
Used in construction, as crushed stone for road bases, in manufacturing railroad ballast, as dimension stone, and sometimes in decorative landscaping or countertops.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why ridges formed of quartzite often remain as prominent hills or mountain crests.
Field identification & locations
Can be identified in the field by its hardness (will easily scratch glass and cannot be scratched by a knife) and the fact that it breaks across the quartz grains rather than around them like sandstone. Commonly found worldwide in ancient orogenic belts.
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