metamorphic
Polished river pebble, likely quartzite or chert
Quartzite (mostly SiO₂), possibly chalcedony-rich chert
AI-generated identification · may be incorrectSmooth, rounded, tan-brown, and weakly translucent with a dull-to-waxy luster; likely Mohs hardness 6.5–7, massive microcrystalline structure, and no visible cleavage. Exact identification is limited by the image; a glass-scratch test can help confirm quartz-rich material.
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Physical properties
Smooth, rounded, tan-brown, and weakly translucent with a dull-to-waxy luster; likely Mohs hardness 6.5–7, massive microcrystalline structure, and no visible cleavage. Exact identification is limited by the image; a glass-scratch test can help confirm quartz-rich material.
Formation & geological history
Likely formed from silica-rich sediment that lithified and/or recrystallized, then was naturally rounded by stream or beach abrasion and subsequently polished. Its geological age cannot be determined visually.
Uses & applications
Commonly sold as a decorative pebble, tumbled stone, or craft material; quartzite may also be used as aggregate, paving stone, and dimension stone. This ordinary specimen has little jewelry value.
Geological facts
The rounded shape indicates prolonged abrasion, while the uniform brown color may reflect iron-oxide staining. It could also be a polished jasper or brown chalcedony, which cannot be distinguished confidently from this photograph alone.
Field identification & locations
Look for a glassy fracture, inability to scratch it with a steel knife, and white streak or no streak; acid should produce no reaction. Common source environments include river gravels, beaches, and commercial lapidary supplies.
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