igneous
Weathered iron-rich river pebble
Likely basalt or mafic rock with limonite/goethite staining
AI-generated identification · may be incorrectDark brown, rounded, earthy to dull luster, and apparently fine-grained; likely Mohs hardness 5–6, with no visible cleavage and moderate-to-high density. The rusty color suggests iron-oxide weathering or a ferruginous coating.
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Physical properties
Dark brown, rounded, earthy to dull luster, and apparently fine-grained; likely Mohs hardness 5–6, with no visible cleavage and moderate-to-high density. The rusty color suggests iron-oxide weathering or a ferruginous coating.
Formation & geological history
Probably a water-worn pebble derived from weathered basalt, gabbro, or another iron-rich volcanic rock; its exact geological age cannot be determined from the photograph. Rounding indicates transport in a stream, river, beach, or glacial deposit.
Uses & applications
Primarily a decorative or educational specimen; comparable material may be used as aggregate or crushed stone, but this individual has little industrial value.
Geological facts
Iron oxides such as limonite and goethite commonly form brown, orange, and red weathering rinds on mafic rocks. The smooth shape reflects prolonged abrasion by moving sediment or ice.
Field identification & locations
Look for a dense, fine-grained interior, weak magnetism, and a rusty streak or coating; a fresh broken surface would help distinguish basalt from ironstone or hematite-rich material. Common in river gravels worldwide.
