mineral

Goethite

Goethite (FeO(OH))

AI-generated identification · may be incorrect

Hardness: 5.0-5.5; Color: Black, brownish-yellow, to reddish-brown; Luster: Submetallic, silky, or dull/earthy; Crystal Structure: Orthorhombic; Cleavage: Perfect; Specific Gravity: 3.3-4.3

Hardness: 5
Color: Black, brownish-yellow, to reddish-brown
Luster: Submetallic, silky, or dull/earthy

Identified June 29, 2026More mineral →

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Physical properties

Hardness: 5.0-5.5; Color: Black, brownish-yellow, to reddish-brown; Luster: Submetallic, silky, or dull/earthy; Crystal Structure: Orthorhombic; Cleavage: Perfect; Specific Gravity: 3.3-4.3

Formation & geological history

Formed primarily through the weathering of iron-rich minerals in oxidized zones of ore deposits or as a direct precipitate in marine and bog environments. It is a common component of soil and rust.

Uses & applications

An important ore of iron. Used as a natural earth pigment (brown ochre), in some jewelry as a collector's specimen, and historically as a pigment in cave paintings.

Geological facts

Goethite was named after the German polymath Johann Wolfgang von Goethe. It is the primary mineral in 'limonite' and has been found on the surface of Mars by the Spirit rover.

Field identification & locations

Identified by its characteristic brownish-yellow to ochre-yellow streak, even when the specimen color appears black. Often found in botryoidal (grape-like) or stalactitic habits. Common in bog iron deposits and as a weathering product of pyrite.