metamorphic
Quartzite
Metamorphic rock composed primarily of quartz (SiO2)
Hardness of 7 on the Mohs scale, colors range from white and gray to pink, red, or yellowish due to iron oxide impurities. It typically has a non-foliated, granular texture with a sugary appearance and vitreous to greasy luster.
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Physical properties
Hardness of 7 on the Mohs scale, colors range from white and gray to pink, red, or yellowish due to iron oxide impurities. It typically has a non-foliated, granular texture with a sugary appearance and vitreous to greasy luster.
Formation & geological history
Formed when quartz-rich sandstone or chert is subjected to high heat and pressure, usually associated with tectonic compression in orogenic belts. Geological age varies widely depending on the formation site, ranging from Precambrian to Cenozoic.
Uses & applications
Used extensively in construction as crushed stone for roadbeds, railway ballast, and building facades. Also used to manufacture silica brick, in metallurgy, and occasionally as decorative 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 ranges after the surrounding softer rocks have eroded away.
Field identification & locations
Can be identified in the field by its hardness (it easily scratches glass and cannot be scratched by a knife) and the fact that it breaks across quartz grains rather than around them, unlike sandstone.
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