mineral
Iron-rich concretion or weathered limonite/goethite nodule
Limonite (hydrous iron oxides), commonly dominated by goethite (FeO(OH))
AI-generated identification · may be incorrectEarthy yellow-brown to rusty brown, dull/ochre luster, irregular polygonal cracking, and likely hardness about 4–5.5 Mohs; typically massive and noncrystalline or microcrystalline, with no obvious cleavage.
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Physical properties
Earthy yellow-brown to rusty brown, dull/ochre luster, irregular polygonal cracking, and likely hardness about 4–5.5 Mohs; typically massive and noncrystalline or microcrystalline, with no obvious cleavage.
Formation & geological history
Formed by oxidation and hydration of iron-bearing minerals during weathering, often as a soil or sedimentary concretion; commonly Quaternary to much older depending on its host deposit.
Uses & applications
Used historically as iron ore and yellow-brown pigment; attractive pieces are collected, but it has little jewelry value because it is opaque and relatively soft.
Geological facts
The term “limonite” is a field name rather than a single precisely defined mineral; its color comes from hydrated iron oxides and hydroxides.
Field identification & locations
Identify it by its ochre streak, earthy texture, high apparent density, and possible attraction to a strong magnet if magnetite is mixed in; common in weathered soils, laterites, ironstone, and sedimentary beds.
