mineral
Goethite
Goethite (FeO(OH))
AI-generated identification · may be incorrectHardness on Mohs scale is 5 to 5.5. Color ranges from yellowish-brown, reddish-brown, to dark brown or black. Luster is adamantine, silky, or dull. Crystal structure is orthorhombic. Cleavage is perfect in one direction. Specific gravity is 3.3 to 4.3.
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Physical properties
Hardness on Mohs scale is 5 to 5.5. Color ranges from yellowish-brown, reddish-brown, to dark brown or black. Luster is adamantine, silky, or dull. Crystal structure is orthorhombic. Cleavage is perfect in one direction. Specific gravity is 3.3 to 4.3.
Formation & geological history
Forms as a weathering product of other iron-rich minerals, often in soils, laterites, and bog iron deposits. Can also form as a primary precipitate in hydrothermal veins and hot springs.
Uses & applications
Used as an iron ore, a pigment (ochre), in gemstone or mineral collections, and occasionally cut into cabochons.
Geological facts
Goethite is named after the famous German poet, novelist, and polymath Johann Wolfgang von Goethe, who was an avid mineralogist. It is one of the most common iron oxides on Earth and is the primary coloring agent in cave paintings and many soils.
Field identification & locations
Can be identified by its characteristic yellowish-brown streak, botryoidal or stalactitic habits, and dark brown to black metallic or velvety luster. Commonly found worldwide in oxidized zones of ore deposits.
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