sedimentary

Iron-rich concretion or weathered ironstone pebble

Goethite/limonite-bearing ironstone; commonly an iron-oxide concretion (FeO(OH)·nH₂O, variable)

AI-generated identification · may be incorrect

Dark brown, opaque, earthy to submetallic luster, rounded and fine-grained with no visible crystals; estimated Mohs hardness 4–6, specific gravity commonly 3–4. A photograph cannot confirm mineral identity, and the pale flecks may be matrix or weathering products.

Identified August 26, 2026More sedimentary →

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At a glance

Common name: Iron-rich concretion or weathered ironstone pebble
Scientific name: Goethite/limonite-bearing ironstone; commonly an iron-oxide concretion (FeO(OH)·nH₂O, variable)
Category: sedimentary
Identified: August 26, 2026
Method: Standard

AI Estimated Value

Usually $1–$10 for an ordinary pebble; approximately $10–$50 for an unusually shaped, heavy, or locality-labeled specimen.

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 oxides and hydroxides around a nucleus, followed by burial, lithification, and river or surface abrasion. Such concretions can form from relatively young sediments through ancient sedimentary sequences.

Uses & applications

Used historically as low-grade iron ore and pigment; attractive pieces are mainly teaching or lapidary specimens, with little jewelry use unless polished.

Geological facts

Goethite and limonite commonly produce brown, yellow-brown, or rusty red colors; hematite-rich material is typically redder or more metallic. A reddish-brown streak on unglazed porcelain and attraction to a strong magnet can help distinguish iron-rich material.

Field identification & locations

Common in weathered soils, stream gravels, sandstone, and ironstone deposits worldwide, including Australia, Brazil, India, and the United States. Confirm with streak, magnetism, hardness, and ideally specific-gravity or laboratory testing.