metamorphic
Quartzite Pebble
Metamorphic Quartzite
Hardness of 7 on the Mohs scale, colors ranging from white and gray to pink or reddish due to iron oxide impurities, vitreous to greasy luster, massive or granular crystal structure, lacking visible cleavage and fracturing conchoidally, with a specific gravity around 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, colors ranging from white and gray to pink or reddish due to iron oxide impurities, vitreous to greasy luster, massive or granular crystal structure, lacking visible cleavage and fracturing conchoidally, with a specific gravity around 2.65.
Formation & geological history
Formed from quartz-rich sandstone or chert that has been subjected to high heat and pressure, typically through regional or contact metamorphism. This geological process recrystallizes the quartz grains into a dense, interlocking mosaic.
Uses & applications
Used in construction, as road aggregate, railroad ballast, dimension stone, and for the production of ferrosilicon and silica bricks.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why quartz-rich rocks often survive long journeys in riverbeds or beaches to become smooth pebbles.
Field identification & locations
Can be identified in the field by its extreme hardness (it will easily scratch glass and cannot be scratched by a steel knife) and the characteristic sugary texture of fractured surfaces where individual quartz crystals break.
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