metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale, typically gray, white, or purplish hues, 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, typically gray, white, or purplish hues, 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 associated with tectonic compression, typically during regional metamorphism over millions of years.
Uses & applications
Used in construction, as crushed stone for road bases, railway ballast, manufacturing of silica brick, and sometimes as a decorative stone or in countertops.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why mountains made of quartzite often stand out as high ridges.
Field identification & locations
Can be identified in the field by its hardness (scratches glass easily) and the fact that it breaks across the quartz grains rather than around them like sandstone. Found worldwide.
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