metamorphic
Quartzite Cobble
Quartzite
Hardness 7 on Mohs scale; light tan to grey color with subtle brownish banding; dull to vitreous luster; granular crystalline structure with fused quartz grains; sub-rounded cobble shape.
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Physical properties
Hardness 7 on Mohs scale; light tan to grey color with subtle brownish banding; dull to vitreous luster; granular crystalline structure with fused quartz grains; sub-rounded cobble shape.
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone, where intense heat and pressure fuse quartz grains together. Later eroded, rounded by water action, and transported in riverbeds or glacial deposits.
Uses & applications
Commonly used as river rock in landscaping, construction aggregate, decorative garden stones, and erosion control.
Geological facts
Quartzite is extremely tough and durable, often outlasting surrounding softer rocks during weathering, resulting in smooth, rounded stream cobbles like this specimen.
Field identification & locations
Identify by its smooth rounded surface, extreme hardness (scratches glass easily), and granular interlocking texture. Commonly found in stream beds, glacial tills, and gravel pits worldwide.
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