mineral
Iron-rich concretion (likely limonite/goethite)
Limonite–goethite aggregate; commonly hydrated iron oxides, approximately FeO(OH)·nH₂O
AI-generated identification · may be incorrectRust-red to brown, earthy-to-submetallic luster, botryoidal/irregular surface, and no visible crystal faces; hardness about 4–5.5 Mohs, specific gravity roughly 3.0–4.3, with typically poor or indistinct cleavage.
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Physical properties
Rust-red to brown, earthy-to-submetallic luster, botryoidal/irregular surface, and no visible crystal faces; hardness about 4–5.5 Mohs, specific gravity roughly 3.0–4.3, with typically poor or indistinct cleavage.
Formation & geological history
Forms when iron-bearing minerals weather and oxidize in soil, sediments, cavities, or near hydrothermal deposits; it is generally geologically young relative to its host rock and may continue forming today.
Uses & applications
Used historically as iron ore and natural ochre pigment; attractive pieces are collected, but this specimen appears mainly of modest educational value rather than jewelry grade.
Geological facts
Limonite is a field name for mixed hydrated iron oxides rather than a single precisely defined mineral. Goethite commonly produces the brown, yellow, and reddish coatings and botryoidal masses associated with limonite.
Field identification & locations
Identify it by its rusty color, heavy feel, earthy streak, and tendency to leave a yellow-brown to reddish-brown streak; a magnet may show weak attraction if magnetite is present. Common in weathered iron deposits, soils, bogs, and sedimentary environments.
