sedimentary

Weathered iron-rich rock, likely ironstone or limonite-bearing concretion

Ironstone/limonite-rich concretion; mainly goethite FeO(OH), hematite Fe₂O₃, and hydrated iron oxides

AI-generated identification · may be incorrect

Dark reddish-brown, earthy to dull luster, irregularly rounded from weathering; estimated Mohs hardness 4–6, with no obvious cleavage and variable density. The pale crust may represent quartz, clay, or weathering residue.

Identified August 27, 2026More sedimentary →

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At a glance

Common name: Weathered iron-rich rock, likely ironstone or limonite-bearing concretion
Scientific name: Ironstone/limonite-rich concretion; mainly goethite FeO(OH), hematite Fe₂O₃, and hydrated iron oxides
Category: sedimentary
Identified: August 27, 2026
Method: Standard

AI Estimated Value

Typically $1–$15 for an ordinary hand specimen; unusual shapes or locality-proven examples may sell for $20–$50.

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 precipitation and cementation of iron oxides in sediment, soil, or groundwater, then rounded by erosion; age cannot be determined from the image. Such concretions commonly develop in weathering zones and sedimentary formations.

Uses & applications

Used historically as a low-grade iron ore and pigment; mainly a curiosity or teaching specimen today, with little jewelry or construction use.

Geological facts

Iron oxides produce the characteristic rust-red to brown color and may leave a reddish-brown streak on unglazed porcelain. A strong magnet response would suggest magnetite or maghemite, though none is visually confirmed.

Field identification & locations

Common in iron-rich soils and sedimentary regions worldwide, including Australia, India, Brazil, and the United States. Field tests include streak, hardness, density, magnetism, and checking for a metallic versus earthy interior.