mineral

Pisolithic limonite/goethite pebble (ironstone)

Hydrated iron oxides, chiefly goethite (α-FeO(OH)) and limonite (FeO(OH)·nH₂O)

AI-generated identification · may be incorrect

Brown, opaque, dull to earthy luster; rounded and likely waterworn, with small surface pits. Hardness about 4–5.5 Mohs, no obvious cleavage, variable specific gravity roughly 3.0–4.3; internal concentric pisolitic texture would require cutting.

Identified August 16, 2026More mineral →

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Physical properties

Formation & geological history

Forms by intense weathering and oxidation of iron-bearing rocks, producing ironstone or lateritic concretions; age may range from recent soil formation to ancient deposits. The image alone cannot establish a precise geological age.

Uses & applications

Used historically as iron ore and occasionally as pigment; attractive polished pieces are mainly collector specimens or curiosities rather than jewelry gemstones.

Geological facts

Limonite is a field term for mixtures of hydrated iron oxides, not a single precisely defined mineral. Its dark brown streak and reddish-yellow powder commonly distinguish it from ordinary basalt or slag.

Field identification & locations

Common in laterite, gossan zones, stream gravels, and weathered iron deposits worldwide. A streak test on unglazed porcelain, magnetism test, and a fresh broken surface are useful; it may resemble meteorite material but usually has an earthy streak and vesicular weathering.