mineral

Goethite (Iron Ore)

Goethite (FeO(OH))

Hardness: 5.0-5.5 on Mohs scale; Color: yellowish-brown to dark brown or black; Luster: Adamantine, silky, or dull/earthy; Crystal system: Orthorhombic; Specific Gravity: 3.3 to 4.3.

Hardness: 5
Color: yellowish-brown to dark brown or black
Luster: Adamantine, silky, or dull/earthy

Identified February 14, 2026More mineral →

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Physical properties

Hardness: 5.0-5.5 on Mohs scale; Color: yellowish-brown to dark brown or black; Luster: Adamantine, silky, or dull/earthy; Crystal system: Orthorhombic; Specific Gravity: 3.3 to 4.3.

Formation & geological history

Formed as a secondary mineral through the weathering and oxidation of other iron-rich minerals like pyrite or magnetite. It is common in soil and bog iron deposits, often found in Gossans (weathered rock covering ore deposits).

Uses & applications

Primarily used as a minor ore of iron. Fine specimens are used in pigment production (Brown Ochre). Botryoidal or iridescent forms are popular among mineral collectors.

Geological facts

Goethite was named after the German polymath and poet Johann Wolfgang von Goethe. It is one of the main components of rust and is a significant constituent of the Martian surface, giving the planet its red color.

Field identification & locations

Identify in the field by its characteristic yellowish-brown streak on a porcelain plate and its high density compared to common silicate rocks. Commonly found in karst landscapes and sedimentary iron basins.