sedimentary

Ironstone concretion (likely limonite/goethite-rich)

Iron-oxide/oxyhydroxide-rich concretion, chiefly goethite (FeO(OH)) and limonite; identification from the photo is provisional

AI-generated identification · may be incorrect

Ochre-brown, earthy to dull luster, irregular knobbly surface; commonly about 4–6 Mohs hardness, with no obvious cleavage. The image does not show enough detail to determine crystal structure or confirm composition.

Identified October 6, 2026More sedimentary →

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At a glance

Common name: Ironstone concretion (likely limonite/goethite-rich)
Scientific name: Iron-oxide/oxyhydroxide-rich concretion, chiefly goethite (FeO(OH)) and limonite; identification from the photo is provisional
Category: sedimentary
Identified: October 6, 2026
Method: Standard

AI Estimated Value

About $2–$20 USD for a common hand-sized specimen; unusual form, locality, or confirmed mineral content may affect value.

Not an official valuation

AI estimate for general interest only — not an appraisal. Actual value depends on condition, provenance, and market demand. Verify with a professional before buying, selling, or insuring.

This identification was generated by AI and may contain errors. Verify important details before relying on them — and never use an AI result to judge whether a specimen is safe to handle. Read the full disclaimer

Physical properties

Formation & geological history

Iron oxides precipitate and cement sediment around a nucleus, forming a concretion during or after burial; such deposits occur across many geological ages and sedimentary settings.

Uses & applications

Commonly collected as a geological specimen; iron-rich material has historically served as iron ore and earthy pigment, though this piece’s grade is unknown.

Geological facts

Goethite and related iron oxides produce yellow, brown, and reddish colors in soils and rocks.

Field identification & locations

Look for a heavy-feeling, rusty-brown specimen that may leave an ochre streak; confirm with a streak test and mineralogical analysis. Ironstone occurs widely in sedimentary basins worldwide.