sedimentary

Ironstone concretion (possible limonite/goethite-rich piece)

Iron-oxide-rich ironstone; commonly composed of goethite (FeO(OH)) and/or limonite

AI-generated identification · may be incorrect

Rough, irregular, dark brown with rusty ochre patches and a dull to slightly earthy luster. Hardness and density cannot be reliably determined from the image; ironstone is typically opaque and non-cleaving.

Identified September 26, 2026More sedimentary →

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At a glance

Common name: Ironstone concretion (possible limonite/goethite-rich piece)
Scientific name: Iron-oxide-rich ironstone; commonly composed of goethite (FeO(OH)) and/or limonite
Category: sedimentary
Identified: September 26, 2026
Method: Standard

AI Estimated Value

About $1–$10 for a small, common, unverified specimen; higher values require distinctive features or confirmed provenance.

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 by iron oxides cementing sediment or precipitating from iron-rich groundwater. Such deposits form in many geological periods and environments; age and exact origin cannot be determined visually.

Uses & applications

Usually collected as a geological curiosity; iron-rich ores have been used as sources of iron pigment and, where sufficiently concentrated, iron ore.

Geological facts

The name “limonite” refers to a variable mixture of hydrated iron oxides rather than a single mineral species.

Field identification & locations

Rust-brown color and earthy surface suggest iron oxides, but a photograph cannot confirm the identification; inspect a fresh surface and streak, or have it tested. Ironstone occurs widely in sedimentary formations worldwide.