sedimentary

Iron-rich concretion (probable hematite/limonite nodule)

Goethite–hematite concretion; FeO(OH) and Fe₂O₃, possibly with quartz/clay

AI-generated identification · may be incorrect

Dark brown, earthy to subtly granular, dull-to-submetallic luster; likely Mohs hardness 4–6 and moderate-to-high specific gravity (~3.3–5.3). No visible crystal faces or cleavage; the rounded form suggests a concretion or weathered nodule.

Identified August 17, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when iron minerals precipitate and cement sediment around a nucleus, commonly in soils, sandstones, lake beds, or weathering zones; age depends on its host deposit and cannot be determined from the image.

Uses & applications

Usually a common geological specimen with little commercial value; iron oxides are important ores and pigments, but this small nodule is generally unsuitable for industry or jewelry.

Geological facts

A reddish-brown streak on unglazed porcelain would support hematite/goethite identification; magnetism may indicate magnetite, though hematite is commonly weakly magnetic or nonmagnetic.

Field identification & locations

Common in iron-rich soils and sedimentary formations worldwide, including the Great Lakes region, western United States, Australia, and Brazil. Test streak, density, hardness, and magnetism; visual identification alone is uncertain.