sedimentary or metamorphic

Rounded river pebble, likely quartz-rich sandstone or fine-grained quartzite

Indeterminate quartz-rich lithic clast; likely quartz sandstone (SiO₂-rich) or quartzite

AI-generated identification · may be incorrect

Brown-gray, smoothly water-worn, dull to slightly satin luster, opaque, and fine-grained; apparent hardness roughly 6–7 Mohs, with no visible cleavage. Exact identification requires a fresh surface, streak, acid, and texture tests.

Identified August 15, 2026More sedimentary or metamorphic →

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Physical properties

Formation & geological history

Likely formed from cemented sand, or metamorphosed sandstone if quartzite, then rounded by stream or beach abrasion; age cannot be determined from the photograph.

Uses & applications

As an individual pebble it has negligible commercial value, though similar quartzite is used as aggregate, paving stone, landscaping rock, and occasionally ornamental material.

Geological facts

The rounded shape records prolonged transport in moving water or surf. A glassy fracture and resistance to scratching by steel favor quartzite; gritty visible grains and weaker cohesion favor sandstone.

Field identification & locations

Common in riverbeds, beaches, and glacial deposits worldwide; test with a steel nail, observe grain texture, and apply dilute hydrochloric acid only if carbonate cement is suspected. Estimated value: $0–$5 as a common specimen.