Goethite

Physical Properties

Hardness: 5-5.5 (Mohs), Color: Yellowish-brown to dark brown or black, Luster: Dull to submetallic, Crystal Structure: Orthorhombic, Streak: Brownish-yellow, Specific Gravity: 3.3-4.3

Formation & Geological History

Formed primary as a weathering product of other iron-rich minerals in oxidized zones of ore deposits. It is a major component of bog iron ore and ironstone.

Uses & Applications

Primary ore of iron; historically used as a pigment (brown ochre) and occasionally as a collector's specimen.

Geological Facts

Named after the German polymath Johann Wolfgang von Goethe. It is one of the most common forms of rust found in nature and has been detected on the planet Mars by the Spirit rover.

Field Identification & Locations

Identified by its signature yellowish-brown streak on a porcelain plate and its high density. Common in soil and weathered rock outcrops globally.

Identified on: 5/15/2026

Mode: Standard