mineral

Botryoidal Goethite

Goethite (α-Fe3+O(OH))

Hardness: 5.0-5.5; Color: Black, brownish-black; Luster: Submetallic, dull, or silky; Crystal structure: Orthorhombic (often botryoidal or acicular); Cleavage: Perfect in one direction; Specific gravity: 3.3-4.3

Hardness: 5
Color: Black, brownish-black
Luster: Submetallic, dull, or silky

Identified February 21, 2026More mineral →

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Physical properties

Formation & geological history

Formed as a secondary mineral in the oxidation zones of iron ore deposits, often as a weathering product of other iron minerals like pyrite or siderite. Found in soil and bog iron ore environments.

Uses & applications

Primary source of iron ore; historically used as a brown ochre pigment; polished specimens are used by collectors and in lapidary work.

Geological facts

Named after the German philosopher and poet Johann Wolfgang von Goethe. It is the main component of iron rust and a common soil constituent ubiquitous across the Earth's crust.

Field identification & locations

Identify by its bubbly (botryoidal) texture, extreme darkness, and characteristic yellowish-brown streak on a porcelain plate. Commonly found in large deposits in the Appalachian Mountains and Michigan in the USA.