sedimentary

Rounded iron-rich river pebble

Likely ferruginous sandstone or ironstone; exact identification requires testing

AI-generated identification · may be incorrect

Brown to reddish-brown, fine-grained, dull earthy luster, rounded and smoothed by abrasion, with small pits and possible quartz grains. Likely hardness about 5–7 Mohs and moderate-to-high density; no visible cleavage or crystals.

Identified August 26, 2026More sedimentary →

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Physical properties

Formation & geological history

Probably weathered and water-transported sedimentary material, later cemented or stained by iron oxides; age cannot be determined from the image. Its rounded form indicates prolonged stream, beach, or glacial abrasion.

Uses & applications

Primarily a landscaping, teaching, or collection specimen; ironstone and ferruginous sandstone may be used locally as aggregate or building stone, but this individual has little commercial value.

Geological facts

Iron oxides such as hematite and goethite commonly produce the rusty brown coloration. The smooth surface and subdued texture are characteristic of a natural cobble rather than a crystal or gemstone.

Field identification & locations

Common in river gravels, beaches, and glacial deposits worldwide. A streak test, magnet test, acid test, and close-grained inspection can distinguish ironstone from basalt, chert, or ordinary sandstone.