mineral

Limonite (Ironstone)

Goethite/Limonite (Hydrated iron(III) oxide-hydroxide)

AI-generated identification · may be incorrect

Hardness: 4 to 5.5 on Mohs scale; Color: Yellowish-brown to dark brown or black; Luster: Dull, earthy, or submetallic; Crystal Structure: Amorphous or microcrystalline; Streak: Yellow-brown.

Hardness: 4 to 5
Color: Yellowish-brown to dark brown or black
Luster: Dull, earthy, or submetallic

Identified May 25, 2026More mineral →

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Physical properties

Hardness: 4 to 5.5 on Mohs scale; Color: Yellowish-brown to dark brown or black; Luster: Dull, earthy, or submetallic; Crystal Structure: Amorphous or microcrystalline; Streak: Yellow-brown.

Formation & geological history

Formed usually by the oxidation and hydration of iron-rich mineral deposits (like pyrite) in the weathering zone. It is a secondary mineral found in sedimentary beds and bog iron deposits.

Uses & applications

Historically used as an iron ore; currently used as a pigment in paints (yellow ochre) and as a low-value collector specimen.

Geological facts

Limonite is not a true mineral but a mixture of hydrated iron oxides. It was once the primary source of iron for early civilizations and was used by prehistoric humans as an art pigment.

Field identification & locations

Identify by its characteristic yellowish-brown streak on a porcelain plate and its earthy appearance. Commonly found in gossans (weathered tops of ore deposits) or as bog iron.