metamorphic
Quartzite Pebble
Metamorphic Quartzite
Hardness of 7 on the Mohs scale, colors typically range from white to gray, pink, or yellowish-brown due to iron impurities. Luster is vitreous to greasy on fractured surfaces, crystal structure is trigonal (microcrystalline quartz grains fused together), cleavage is absent, specific gravity is around 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, colors typically range from white to gray, pink, or yellowish-brown due to iron impurities. Luster is vitreous to greasy on fractured surfaces, crystal structure is trigonal (microcrystalline quartz grains fused together), cleavage is absent, specific gravity is around 2.65.
Formation & geological history
Formed from quartz-rich sandstone subjected to high heat and pressure during regional or contact metamorphism, typically during mountain-building events over millions of years.
Uses & applications
Used in construction, road aggregate, manufacturing of railway ballast, and occasionally for decorative landscaping or lapidary work.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why quartz-rich rocks often survive as pebbles in rivers and beaches long after other rocks have eroded away.
Field identification & locations
Can be identified in the field by its high hardness (scratches glass easily), lack of reactivity to acid, and a sugary texture on broken surfaces where quartz crystals break through rather than around grains.
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