metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale, color ranges from white and gray to pink, yellow, or green due to impurities, vitreous to greasy luster, massive to granular crystal structure, lacks prominent cleavage, and has a specific gravity of roughly 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, color ranges from white and gray to pink, yellow, or green due to impurities, vitreous to greasy luster, massive to granular crystal structure, lacks prominent cleavage, and has a specific gravity of roughly 2.65.
Formation & geological history
Formed when quartz-rich sandstone is subjected to high heat and pressure, typically through tectonic compression in orogenic belts. Can range in geological age from Precambrian to Cenozoic.
Uses & applications
Used widely in construction for road aggregate, railroad ballast, dimension stone, and manufactured countertops, as well as in the production of silica brick and ferrosilicon.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why ridges formed of quartzite often persist as prominent mountain crests and hills.
Field identification & locations
Can be identified in the field by its hardness (it 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, unlike sandstone.
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