Goethite
Image: <a href="//commons.wikimedia.org/wiki/User:Strekeisen" title="User:Strekeisen">Strekeisen</a> (CC BY-SA 4.0)
Mineral NameGoethite
Chemical FormulaFeO(OH)
Mohs Hardness5
Crystal Systemorthorhombic
Streak Coloryellowish-brown
Cleavageperfect on {010}, good on {100}
Fractureuneven/splintery
Specific Gravity3.3
Colorsreddish-brown, yellowish-brown, orange-brown
Transparencytranslucent
Type LocalityNot specified
Mineral GroupOxides/Hydroxides
Usesiron ore, pigment, collector's mineral
Associated Mineralsplagioclase, pyroxene, olivine
Raritycommon
Description
This microscopic image displays concentric, laminated structures of reddish-brown to yellowish-brown iron hydroxides, likely filling a void or fracture within a fine-grained basalt matrix.
Geological Context
Goethite forms as a common secondary mineral through the weathering and alteration of primary iron-bearing minerals in various rocks, including basalt, often in oxidizing environments. It can occur as a precipitate in vesicles or fractures.
