mineral
Goethite
Goethite (FeO(OH))
Hardness: 5-5.5 (Mohs), Color: brownish-black, yellowish-brown, Luster: Adamantine to dull, Crystal structure: Orthorhombic, Cleavage: Perfect on {010}, Streak: Brownish-yellow
- Hardness
- 5-5
- Streak
- Brownish-yellow
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Physical properties
Hardness: 5-5.5 (Mohs), Color: brownish-black, yellowish-brown, Luster: Adamantine to dull, Crystal structure: Orthorhombic, Cleavage: Perfect on {010}, Streak: Brownish-yellow
Formation & geological history
Formed usually through the weathering of other iron-rich minerals like pyrite or magnetite. It is a common component of soil and bog iron ore, creating under oxidizing conditions.
Uses & applications
Historically used as an iron ore; currently used as a pigment (brown ochre) and as a mineral specimen for collectors.
Geological facts
Named after the German polymath and poet Johann Wolfgang von Goethe. It is a primary component of rust and exists on the planet Mars.
Field identification & locations
Identified in the field by its distinct yellowish-brown streak and botryoidal (grape-like) or massive habit. Found worldwide in weathered zones of iron deposits.
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sedimentary
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Metamorphic
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Gypsum (variety Selenite or Alabaster)
Calcium sulfate dihydrate (CaSO4·2H2O)
Mineral
Nephrite Jade
Nephrite
Mineral/Rock
Granite
Granite (Phaneritic intrusive igneous rock)
igneous