metamorphic

Rounded quartz-rich cobble, likely quartzite or quartz sandstone

Quartzite (mostly SiO₂); possibly ferruginous quartz sandstone

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; tan, pink, and rusty-red coloration from iron oxides; typically dull to glassy luster, granular texture, and no obvious cleavage. Dense and resistant, with quartz grains commonly fused together in quartzite.

Identified September 21, 2026More metamorphic →

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Physical properties

Formation & geological history

If quartzite, it formed when quartz sandstone was metamorphosed under heat and pressure, commonly during Precambrian to younger mountain-building events; sandstone formed earlier by sediment deposition and lithification. The smooth surface indicates prolonged stream, beach, or glacial abrasion.

Uses & applications

Used as durable aggregate, landscaping stone, paving, and building material; attractive pieces may be polished for décor or collected, though this rounded specimen has limited jewelry value.

Geological facts

Iron staining produces the orange, pink, and red tones; quartz-rich cobbles often survive weathering after softer surrounding rocks erode.

Field identification & locations

Look for a very hard, quartz-rich stone that scratches glass and resists steel; quartzite breaks across grains rather than crumbling around them. Common in river gravels and glacial deposits worldwide.