Goethite - FeO(OH)

Habit: Crystals prismatic and striated, also flattened into tablets or scales. Usually massive as reniform, botryoidal, or stalactitic masses with radial-fibrous structure. Opaque, transparent on thin edges, Adamantine to Metallic Luster, sometimes dull, earthy, also silky.

Environment: A common weathering product derived from numerous iron-bearing minerals in oxygenated environments; especially siderite, pyrite, magnetite and glauconite. Widespread as a deposit in bogs and springs ("bog iron ore"). Also the principal component of common rust everywhere where iron and steel objects have been subject to corrosion.

Etymology: Named for Johann Wolfgang von Goethe (1749-1832), German poet, philosopher, and naturalist.