mineral

Ironstone concretion (likely hematite–limonite nodule)

Massive hematite (Fe₂O₃) and goethite/limonite (FeO(OH)·nH₂O), possibly an iron-rich concretion

AI-generated identification · may be incorrect

Dark reddish-brown, earthy to submetallic luster, irregular botryoidal/lobate surface, and no visible crystal faces or cleavage. Hematite hardness is about 5–6.5 Mohs; limonite/goethite commonly 4–5.5, with a red-brown streak and high density.

Identified August 23, 2026More mineral →

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At a glance

Common name: Ironstone concretion (likely hematite–limonite nodule)
Scientific name: Massive hematite (Fe₂O₃) and goethite/limonite (FeO(OH)·nH₂O), possibly an iron-rich concretion
Category: mineral
Identified: August 23, 2026
Method: Standard

AI Estimated Value

About $5–$30 for a common hand specimen; $30–$150 for unusually large, aesthetic, or locality-labeled pieces.

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 groundwater precipitation and oxidation of iron minerals, producing a concretionary or botryoidal mass; exact age cannot be determined from the image. Such nodules occur in weathered sedimentary rocks, soils, and hydrothermal environments.

Uses & applications

Used as iron ore where sufficiently pure, and historically as a red-brown pigment; attractive specimens are collected but are generally low-value.

Geological facts

A diagnostic test is streak: hematite leaves red to reddish-brown, while goethite/limonite tends to leave yellow-brown. Its knobby form may resemble kidney ore, a botryoidal hematite variety.

Field identification & locations

Common in iron-rich soils and sedimentary districts worldwide, including the Lake Superior region, Brazil, Australia, and the United Kingdom. A magnet test may be weak or absent unless magnetite is also present.