sedimentary

Weathered iron-rich river pebble

Ferruginous chert or ironstone pebble; exact identification requires testing

AI-generated identification · may be incorrect

Brown to ochre, rounded and naturally smoothed, with dull to weakly earthy luster and scattered dark iron-oxide spots. Likely hardness about 5–7 Mohs; fine-grained, massive, and non-cleavable, with possible magnetism if magnetite is present.

Identified September 14, 2026More sedimentary →

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Physical properties

Formation & geological history

Probably formed from silica-rich or iron-rich sediment that lithified and was later chemically weathered and rounded by stream or coastal transport. Its precise geological age and original formation environment cannot be determined from the image alone.

Uses & applications

Primarily a collecting specimen or decorative pebble; ferruginous chert may be used locally as aggregate or road material, while ironstone can be an iron ore if sufficiently iron-rich.

Geological facts

The rusty coloration commonly comes from hematite and goethite coatings or cement. A streak, hardness, density, magnetism, and acid test would distinguish chert, ironstone, and weathered basalt.

Field identification & locations

Common in gravel beds, river channels, beaches, and glacial deposits worldwide. Test whether it scratches glass, leaves a red-brown streak, attracts a magnet, or fizzes with dilute hydrochloric acid.