sedimentary

Rounded iron-rich river pebble

Likely ferruginous sandstone or ironstone; exact identification requires testing

AI-generated identification · may be incorrect

Dark reddish-brown to gray, dull earthy luster, fine-grained and strongly water-worn; apparent hardness about 5–7 Mohs, with no visible cleavage. The rusty color likely reflects hematite/goethite cement or coatings; specific gravity is moderate to high.

Identified August 29, 2026More sedimentary →

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Physical properties

Formation & geological history

Probably formed from iron-bearing sediment that lithified and was later rounded by stream or beach transport; age cannot be determined from the image. Surface pits and weathering may reflect dissolution or abrasion.

Uses & applications

Primarily a natural-history or decorative specimen; ironstone and ferruginous sandstone may be used locally as aggregate or building stone, but this rounded piece has little industrial value.

Geological facts

The smooth shape indicates prolonged mechanical abrasion, while the dark gray interior and red-brown weathering rind suggest variable oxidation of iron minerals.

Field identification & locations

Look for a rusty red streak, dense feel, and possible attraction to a strong magnet if magnetite is present; a streak test, acid test, and fresh break would distinguish ironstone from basalt or ordinary sandstone. Common in stream gravels and weathered sedimentary terrains.