sedimentary

Likely brown ironstone or limonite-rich rock fragment

Ironstone, chiefly iron oxides/hydroxides such as goethite (α-FeO(OH)) and limonite

AI-generated identification · may be incorrect

Small, rough, opaque brown specimen with an earthy to dull luster; hardness and specific gravity cannot be reliably determined from the photo. Ironstone is commonly massive rather than visibly crystalline, with variable hardness (about 4–6 for goethite-rich material).

Identified September 27, 2026More sedimentary →

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At a glance

Common name: Likely brown ironstone or limonite-rich rock fragment
Scientific name: Ironstone, chiefly iron oxides/hydroxides such as goethite (α-FeO(OH)) and limonite
Category: sedimentary
Identified: September 27, 2026
Method: Standard

AI Estimated Value

About $0–$5 for a small, common fragment; higher value requires a distinctive locality, structure, or documented 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

Iron-rich minerals precipitated or accumulated during weathering and sedimentation; ironstone forms in many geological periods and environments. The specimen’s age and exact formation cannot be determined visually.

Uses & applications

Ironstone has historically been mined as iron ore; small fragments are mainly of educational or modest collector interest.

Geological facts

Brown iron-rich coatings and nodules can form as iron-bearing minerals oxidize near Earth’s surface.

Field identification & locations

Look for a dense, earthy brown fragment that may leave a reddish-brown streak; a streak test and hardness test can help distinguish iron oxides from other rocks. Common ironstone deposits occur worldwide.