mineral
Botryoidal limonite/goethite nodule
Limonite (largely goethite, FeO(OH), with hydrated iron oxides)
AI-generated identification · may be incorrectHardness about 4–5.5 Mohs; mustard-yellow to brown, earthy to dull/submetallic luster, opaque, with rounded botryoidal surfaces and no obvious cleavage. Typically has a relatively high specific gravity of about 3.3–4.3.
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Physical properties
Hardness about 4–5.5 Mohs; mustard-yellow to brown, earthy to dull/submetallic luster, opaque, with rounded botryoidal surfaces and no obvious cleavage. Typically has a relatively high specific gravity of about 3.3–4.3.
Formation & geological history
Forms as a secondary iron-oxide deposit through weathering and oxidation of iron-bearing minerals, commonly in soils, veins, cavities, and hydrothermal or sedimentary environments. Its age depends on the host deposit and may range from recent weathering to ancient geological formations.
Uses & applications
Used historically as an iron ore and yellow-brown pigment; attractive botryoidal specimens are collected, but this example is generally of modest market value.
Geological facts
The name limonite describes a mixed, poorly crystalline iron-oxide material rather than one precisely defined mineral. Yellow interiors or streaks can reflect goethite, while darker zones may contain hematite or manganese oxides.
Field identification & locations
Identify it by its ochre-brown color, heavy feel, earthy yellow-brown streak, and rounded crusty texture; it should not fizz in dilute acid. Common worldwide, especially in weathered iron deposits and oxidized ore zones.
