metamorphic
Quartzite Cobble / Quartz River Pebble
Silicon Dioxide (SiO2) - Quartzite / Quartz
Hardness 7 on the Mohs scale, waxy to vitreous luster, sub-translucent to opaque, light tan to brownish-grey color due to iron oxide staining, conchoidal to uneven fracture, highly weather-resistant
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Physical properties
Hardness 7 on the Mohs scale, waxy to vitreous luster, sub-translucent to opaque, light tan to brownish-grey color due to iron oxide staining, conchoidal to uneven fracture, highly weather-resistant
Formation & geological history
Formed from quartz-rich sandstone subjected to high metamorphic temperatures and pressure, fusing quartz sand grains together. Subsequently rounded and smooth-weathered by river, stream, or glacial action.
Uses & applications
Used in aggregate construction, landscaping, road base, river rock decor, and mineral specimen collecting.
Geological facts
Quartzite is exceptionally tough and durable, often outlasting surrounding rock formations during weathering. River-worn cobbles like this can travel hundreds of miles over thousands of years.
Field identification & locations
Identified by its extreme hardness (scratches glass/steel easily), rounded cobble shape, sugary to waxy texture, and light brownish tint. Extremely common in river beds, gravel pits, and glacial deposits worldwide.
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