mineral
Limonite / Goethite (Ironstone Nodule)
Hydrated Iron(III) Oxide-Hydroxide (FeO(OH)·nH2O)
Hardness: 4-5.5 on Mohs scale. Color: Dark brown, black, to yellowish-brown. Luster: Earthy, sub-metallic, to dull. Crystal Structure: Amorphous or microcrystalline aggregate. Streak: Yellowish-brown.
- Hardness
- 4-5
- Color
- Dark brown, black, to yellowish-brown
- Luster
- Earthy, sub-metallic, to dull
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Physical properties
Hardness: 4-5.5 on Mohs scale. Color: Dark brown, black, to yellowish-brown. Luster: Earthy, sub-metallic, to dull. Crystal Structure: Amorphous or microcrystalline aggregate. Streak: Yellowish-brown.
Formation & geological history
Formed through the weathering and oxidation of iron-rich minerals like pyrite, siderite, or magnetite in sedimentary environments or soil zones. Often forms crusts, concretions, or pseudomorphs.
Uses & applications
Historically used as a minor iron ore and as a natural brown/yellow pigment (ochre). Collected by mineral enthusiasts.
Geological facts
Limonite is not a true single mineral, but a field term for a mixture of hydrated iron oxide minerals, predominantly goethite along with lepidocrocite and jarosite.
Field identification & locations
Identified by its heavy weight for its size, rusty/dark coloration, and characteristic yellowish-brown streak on unglazed porcelain. Common in sedimentary rock beds and soil surfaces worldwide.
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Limonite / Goethite (Iron Ore Mineral nodule)
FeO(OH)·nH2O / FeO(OH)
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