sedimentary

Iron-rich concretion or weathered ironstone

Limonite/goethite-rich ironstone; chiefly hydrated iron oxides (FeO(OH)·nH₂O)

AI-generated identification · may be incorrect

Dark reddish-brown, earthy to submetallic luster, irregular botryoidal surface, and apparent high density; likely Mohs hardness about 4–5.5, with no visible cleavage or distinct crystal faces.

Identified September 8, 2026More sedimentary →

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Physical properties

Dark reddish-brown, earthy to submetallic luster, irregular botryoidal surface, and apparent high density; likely Mohs hardness about 4–5.5, with no visible cleavage or distinct crystal faces.

Formation & geological history

Probably formed by groundwater oxidation and concentration of iron minerals in sediment, producing a concretion or ferruginous nodule; age cannot be determined from the photograph. It may also be heavily weathered hematite or a porous iron-rich rock.

Uses & applications

Common ironstone has limited commercial value but can serve as an educational specimen, pigment source, or lapidary curiosity; iron ores are industrially important when sufficiently concentrated.

Geological facts

A reddish-brown streak on unglazed porcelain would support limonite/goethite, while a red-to-brown streak and greater hardness may indicate hematite. Magnetism, if present, could suggest magnetite-bearing material.

Field identification & locations

Common in soils, sedimentary formations, and weathered iron deposits worldwide; test streak, density, hardness, and magnetism rather than relying on color alone. The image does not show enough detail for a precise species identification.