metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale; usually white, gray, pink, or reddish due to iron oxide impurities; non-foliated texture; vitreous to greasily lustrous; conchoidal fracture.
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Physical properties
Hardness of 7 on the Mohs scale; usually white, gray, pink, or reddish due to iron oxide impurities; non-foliated texture; vitreous to greasily lustrous; conchoidal fracture.
Formation & geological history
Formed when quartz-rich sandstone is subjected to high heat and pressure, typically through tectonic compression in orogenic belts. Geological age can range from Precambrian to Cenozoic.
Uses & applications
Used in construction, as crushed stone for road bases, railway ballast, manufacturing silica brick, and sometimes as a decorative dimension stone or countertops.
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 crests.
Field identification & locations
Can be identified by testing hardness (scratches glass easily) and observing that it fractures across quartz grains rather than around them, unlike sandstone. Found worldwide in ancient mountain ranges.
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