sedimentary

Weathered iron-rich concretion or ironstone cobble

Limonite/goethite-rich ironstone, commonly with hematite and quartz

AI-generated identification · may be incorrect

Dark brown to gray, earthy to dull luster, fine-grained and strongly weathered; approximate Mohs hardness 4–6, with no visible cleavage. The rounded shape and rusty orange surface suggest an iron-rich concretion or naturally water-worn cobble rather than a crystal-rich igneous rock.

Identified September 7, 2026More sedimentary →

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Physical properties

Formation & geological history

Likely formed by precipitation and cementation of iron oxides around a nucleus in sediment, then rounded by stream or beach transport; age cannot be determined from the photograph. Similar ironstone concretions occur in sedimentary basins worldwide.

Uses & applications

Used locally as durable aggregate, pigment source, or decorative stone; generally has little jewelry value unless unusually dense, patterned, or magnetic.

Geological facts

Rust-colored areas are hydrated iron oxides, especially goethite and limonite; darker areas may contain hematite or manganese oxides. A streak test, magnet test, and fresh broken surface would substantially improve identification.

Field identification & locations

Look for a yellow-brown to reddish-brown streak, heavy feel, and possible weak magnetism; ironstone commonly occurs in river gravels, beaches, and sandstone or shale formations. Avoid assuming it is a meteorite: a meteorite typically has a fusion crust, metallic interior, and much higher density.