metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale, grayish-white to brownish color with iron oxide staining, 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, grayish-white to brownish color with iron oxide staining, 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 or contact metamorphism, often billions of years old.
Uses & applications
Used in construction, as road aggregate, in railway ballast, for manufacturing refractory bricks, and occasionally as decorative stone or in lapidary work.
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 ranges.
Field identification & locations
Identified in the field by its high hardness (scratches glass, cannot be scratched by a knife) and the lack of visible pore spaces between grains compared to parent sandstone.
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