Botryoidal Goethite

Physical Properties

Hardness: 5.0-5.5; Color: Dark brown to metallic black, often with an iridescent tarnish; Luster: Submetallic, silky, or dull; Crystal Structure: Orthorhombic (often forming botryoidal or needle-like aggregates); Specific Gravity: 3.3-4.3

Formation & Geological History

Formed as a secondary mineral through the weathering and oxidation of iron-rich primary minerals (such as pyrite or magnetite) in soil and other low-temperature sedimentary environments.

Uses & Applications

A major ore of iron; also used as an earth pigment (brown ochre) and collected as mineral specimens.

Geological Facts

Named after the German polymath Johann Wolfgang von Goethe. It is one of the most common iron oxides on Earth and has even been identified in Martian soil by the Spirit rover.

Field Identification & Locations

Identify in the field by its distinct 'grape-like' (botryoidal) rounded clusters and its yellow-brown streak. Commonly found in gossans (iron hats) above ore deposits.

Identified on: 4/14/2026

Mode: Standard