sedimentary

Ironstone concretion (likely a hematite-rich nodule)

Ferruginous ironstone concretion; iron oxides/hydroxides, chiefly hematite (Fe₂O₃) and/or goethite (FeO(OH))

AI-generated identification · may be incorrect

A rounded, reddish-brown nodule with a concentric, bull’s-eye-like surface pattern, consistent with iron-oxide cemented layers. Hardness and streak cannot be reliably determined from the photo; ironstone commonly has a dull to earthy luster and variable density.

Identified September 27, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms as iron-rich minerals precipitate and cement sediment around a nucleus, often producing concentric bands. The image alone cannot establish its age or exact formation setting.

Uses & applications

Mostly collected as a curiosity or teaching specimen; iron-rich material has industrial uses where deposits are sufficiently extensive, but this small nodule has no practical ore value.

Geological facts

Concentric patterns can form as mineral-rich fluids repeatedly deposit iron oxides around a core. Similar-looking nodules can also form through other mineralization processes, so appearance alone is not definitive.

Field identification & locations

The reddish-brown color and concentric structure support ironstone, but a fresh streak test and examination of a broken surface would help confirm it. Iron-rich rocks are plausible near Sergipe, Brazil; precise local geology is needed to narrow the identification.