metamorphic
Quartzite
Metamorphic Quartz-rich Rock
Hardness of 7 on the Mohs scale, colors range from white to gray, pink, yellowish-brown, and reddish due to iron oxide impurities. It has a vitreous to greasy luster, non-foliated massive crystal structure, and breaks across quartz grains rather than around them.
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Physical properties
Hardness of 7 on the Mohs scale, colors range from white to gray, pink, yellowish-brown, and reddish due to iron oxide impurities. It has a vitreous to greasy luster, non-foliated massive crystal structure, and breaks across quartz grains rather than around them.
Formation & geological history
Formed when quartz-rich sandstone is subjected to high heat and pressure, typically through tectonic compression in orogenic belts. Geological age varies greatly from Precambrian to Cenozoic depending on the specific deposit.
Uses & applications
Used extensively as crushed stone in road construction, railroad ballast, dimension stone for building facings, flooring tiles, and in the manufacture of silica brick and ferrosilicon.
Geological facts
Pure quartzite is one of the most chemically inert and physically durable rocks on Earth, making it extremely resistant to weathering and erosion, which explains why ancient mountain ranges often weather down to ridges of quartzite.
Field identification & locations
Can be identified in the field by its sugary texture on broken surfaces, extreme hardness (scratches glass easily and cannot be scratched by a knife), and lack of fizz when tested with hydrochloric acid. Found worldwide in ancient mountain belts.
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