metamorphic
Quartzite Pebble
Metamorphic Quartzite
Hardness of 7 on the Mohs scale, colors ranging from white and gray to tan and reddish-brown due to iron oxide impurities, vitreous to greasy luster, massive crystal structure with interlocking quartz grains, conchoidal fracture with no true cleavage, and 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 tan and reddish-brown due to iron oxide impurities, vitreous to greasy luster, massive crystal structure with interlocking quartz grains, conchoidal fracture with no true cleavage, and a specific gravity around 2.65.
Formation & geological history
Formed from quartz-rich sandstone or chert that has been subjected to heat and intense pressure through regional or contact metamorphism. The original quartz grains recrystallize along with the cementing material, producing a dense, exceptionally durable rock that resists weathering.
Uses & applications
Used widely in construction for road aggregate, railway ballast, building stone, and manufacturing refractory bricks and silica blocks. Highly polished pieces are also used for decorative landscaping, gravel, and occasionally lapidary work.
Geological facts
Because quartz is extremely resistant to both chemical weathering and physical abrasion, quartzite pebbles often survive long journeys in riverbeds and marine environments, becoming beautifully rounded smooth beach stones.
Field identification & locations
Easily identified in the field by its extreme hardness (it will easily scratch glass and cannot be scratched by a steel knife) and the sugary texture visible on freshly broken surfaces where quartz grains fracture through rather than around.
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