metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale, color ranges from white and grey to pink or reddish due to iron oxide impurities, vitreous to greasy luster, conchoidal fracture, 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 or reddish due to iron oxide impurities, vitreous to greasy luster, conchoidal fracture, specific gravity of 2.65.
Formation & geological history
Formed when quartz-rich sandstone is subjected to high heat and pressure, typically through tectonic compression in orogenic belts, altering the quartz grains into an interlocking mosaic.
Uses & applications
Used in construction, as crushed stone for roadbeds, in the manufacture of railroad ballast, and occasionally as a decorative dimension stone or countertop material.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why mountains made of quartzite often remain prominent while surrounding rock erodes.
Field identification & locations
Can be identified by its inability to be scratched by a knife or glass (hardness 7) and its tendency to fracture across the quartz grains rather than around them, unlike sandstone.
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