metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale, colors ranging from white and gray to pink or yellowish-brown due to iron oxide impurities, vitreous to greasy luster, non-foliated massive crystal structure, conchoidal fracture with no true cleavage, specific gravity of 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, colors ranging from white and gray to pink or yellowish-brown due to iron oxide impurities, vitreous to greasy luster, non-foliated massive crystal structure, conchoidal fracture with no true cleavage, specific gravity of 2.65.
Formation & geological history
Formed when quartz-rich sandstone or chert is subjected to high heat and pressure, typically through tectonic compression during mountain-building events. Geological age varies widely from Precambrian to Cenozoic.
Uses & applications
Used in construction, as crushed stone for road bases, railway ballast, manufacturing silica bricks, and occasionally as an ornamental decorative stone or countertop material.
Geological facts
Because quartz is extremely resistant to weathering, quartzite-rich mountains often form the highest ridges and peaks in an area as surrounding softer rock erodes away.
Field identification & locations
Can be identified in the field by its inability to be scratched by a steel knife, its rough sandpaper-like texture on weathered surfaces, and the fact that it breaks across the quartz grains rather than around them (unlike sandstone).
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