metamorphic
Quartzite
Metamorphic Quartz Arenite
Hardness of 7 on the Mohs scale, typically white to gray or pinkish due to iron oxide impurities, vitreous to greasy luster, massive to granular crystal structure, no good cleavage (fractures conchoidally through quartz grains), specific gravity around 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, typically white to gray or pinkish due to iron oxide impurities, vitreous to greasy luster, massive to granular crystal structure, no good cleavage (fractures conchoidally through quartz grains), specific gravity around 2.65.
Formation & geological history
Formed from quartz-rich sandstone or chert that has been subjected to regional or contact metamorphism involving high temperatures and pressures, recrystallizing the sand grains and the silica cement into an interlocking mosaic of quartz crystals.
Uses & applications
Used in construction as crushed stone for road bases, railroad ballast, decorative aggregates, dimension stone, manufacturing of silica bricks, and occasionally as a gemstone or ornamental stone.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why mountains made of quartzite often form the highest ridges and peaks in an area.
Field identification & locations
Identified by its sugary texture on fractured surfaces and the fact that it will scratch glass and cannot be scratched by a knife blade (hardness 7). It does not fizz with hydrochloric acid.
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