sedimentary

Iron-rich concretion (probable limonite/goethite concretion)

Hydrated iron oxides, chiefly limonite (FeO(OH)·nH₂O) and goethite (FeO(OH))

AI-generated identification · may be incorrect

Hardness about 4–5.5 Mohs; rusty orange-brown, earthy to dull luster, fine-grained and noncrystalline, with no obvious cleavage. The rounded, roughly concentric weathering pattern suggests a concretion rather than a crystal or metallic meteorite.

Identified August 13, 2026More sedimentary →

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At a glance

Common name: Iron-rich concretion (probable limonite/goethite concretion)
Scientific name: Hydrated iron oxides, chiefly limonite (FeO(OH)·nH₂O) and goethite (FeO(OH))
Category: sedimentary
Identified: August 13, 2026
Method: Standard

AI Estimated Value

Typically $1–$15 for a common specimen; unusually large, patterned, or locality-labeled examples may sell for $20–$75.

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

Likely formed when iron-bearing groundwater precipitated around a small nucleus within sediment, producing concentric cementation; later erosion exposed it. Exact geological age cannot be determined from the photograph.

Uses & applications

Usually collected as a geological curiosity or used for teaching; iron-rich concretions have little industrial value compared with iron ore. Not generally suitable for jewelry or construction aggregate.

Geological facts

Limonite is a field term for mixed hydrated iron oxides rather than a single precisely defined mineral. Its rusty color comes from oxidized iron, and some concretions may show a denser, darker interior when broken.

Field identification & locations

Common in sedimentary terrains, weathered soils, sandstone, clay, and former bog or groundwater environments worldwide. Test for a relatively heavy feel, earthy rusty streak, and possible weak attraction to a strong magnet; laboratory testing is needed for a definitive identification.