mineral

Goethite

Goethite (FeO(OH))

Hardness: 5-5.5 (Mohs), Color: Brownish-black to yellowish-brown, Luster: Submetallic to dull, Crystal Structure: Orthorhombic, Cleavage: Perfect on {010}, Specific Gravity: 3.3-4.3.

Hardness: 5-5

Identified May 31, 2026More mineral →

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Physical properties

Hardness: 5-5.5 (Mohs), Color: Brownish-black to yellowish-brown, Luster: Submetallic to dull, Crystal Structure: Orthorhombic, Cleavage: Perfect on {010}, Specific Gravity: 3.3-4.3.

Formation & geological history

Goethite forms under oxidizing conditions as a weathering product of other iron-rich minerals such as pyrite, magnetite, and siderite. It is common in bog iron deposits and lateritic soils.

Uses & applications

Primary ore of iron; used as an earth pigment (ochre) in paints, and occasionally collected as specimens when in botryoidal or iridescent forms.

Geological facts

Named after the German polymath and poet Johann Wolfgang von Goethe. It is one of the most common forms of iron oxide found in nature and is the primary component of rust and limonite.

Field identification & locations

Field identification involves checking for a yellowish-brown streak on a porcelain plate and its characteristic rusty-brown appearance. Common in weathered outcrops and iron-rich soil regions.