metamorphic
Quartzite Pebble
Metamorphic Quartzite (SiO2)
Hardness of 7 on the Mohs scale, colors range from white to gray and tan, 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 range from white to gray and tan, vitreous to greasy luster, massive crystal structure with interlocking quartz grains, conchoidal fracture, specific gravity around 2.65.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone or chert under high heat and tectonic pressure, commonly over hundreds of millions of years.
Uses & applications
Used in landscaping, road construction, railway ballast, manufacturing of silica bricks, and occasionally as decorative stone.
Geological facts
Quartzite is extremely resistant to weathering and chemical erosion, which is why quartz-rich rocks often survive as smooth pebbles in riverbeds and landscapes long after softer rocks have eroded away.
Field identification & locations
Identified by its high hardness (scratches glass easily), lack of effervescence with acid, and sugary texture of interlocking grains visible under magnification. Found globally in ancient metamorphic belts and river gravel deposits.
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