metamorphic
Banded Quartzite
Metamorphosed Quartz Sandstone / Quartzite
Hardness of 7 on the Mohs scale, colors ranging from white to brown and reddish-brown due to iron oxide impurities, vitreous to greasy luster, massive crystal structure with interlocking quartz grains, conchoidal fracture, specific gravity around 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, colors ranging from white to brown and reddish-brown due to iron oxide impurities, vitreous to greasy luster, massive crystal structure with interlocking quartz grains, conchoidal fracture, specific gravity around 2.65.
Formation & geological history
Formed from quartz-rich sandstone or chert that has been subjected to heat and pressure through regional or contact metamorphism, fusing the original sand grains into a dense, interlocking quartz matrix over millions of years.
Uses & applications
Used in landscaping, decorative stone, crushed stone for road construction, and occasionally in lapidary work for cabochons and polished specimens.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why quartz-rich rocks often survive as smooth, rounded pebbles and cobbles in riverbeds and beaches long after less durable minerals have eroded away.
Field identification & locations
Easily identified in the field by its extreme hardness (will scratch glass and cannot be scratched by a steel knife) and the visible sedimentary banding or relict layers that have been completely recrystallized.
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