sedimentary

Rounded quartz-rich cobble

Likely quartzite or quartz-rich sandstone; exact identification requires a fresh break or hardness test

AI-generated identification · may be incorrect

Pale gray-beige, fine-grained, smooth and strongly rounded by transport, with dull to faintly glassy luster. Likely hardness about 6–7 if quartz-rich; massive, with no obvious cleavage and moderate-to-high density.

Identified August 17, 2026More sedimentary →

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Physical properties

Formation & geological history

Probably weathered from a quartz-rich sedimentary or metamorphic source and rounded in a stream, beach, or glacial environment. Its precise geological age cannot be determined visually.

Uses & applications

Primarily a landscaping, garden, decorative, or educational specimen; not generally valuable for construction or jewelry unless unusually pure, colorful, or patterned.

Geological facts

The smooth oval shape records prolonged abrasion and transport. Dark patches may be iron-oxide staining, clay, or minor mafic minerals rather than distinct crystals.

Field identification & locations

Test a concealed edge with a steel knife: quartzite should resist scratching, while sandstone may scratch more easily and reveal visible grains. Common in river gravels, beaches, alluvial deposits, and glacial till.