Goethite
Image: <a href="//commons.wikimedia.org/wiki/User:Archaeodontosaurus" title="User:Archaeodontosaurus">Didier Descouens</a> (CC BY 3.0)
Mineral NameGoethite
Chemical FormulaFeO(OH)
Mohs Hardness5
Crystal Systemorthorhombic
Lusteradamantine
Streak Coloryellowish brown
Cleavageperfect on {010}
Fractureuneven
Specific Gravity3.3
Colorsbrown, dark brown, black
Transparencyopaque
Type LocalityWawa, Chabanel Township, Algoma District, Ontario, Canada
Mineral GroupOxides
Usesiron ore, pigment, collector
Associated Mineralsquartz
Raritycommon
Description
The image displays radiating, acicular to fibrous aggregates of brown goethite crystals, some forming fan-like sprays and others a dense, botryoidal mass, set against a matrix of clear to milky quartz.
Geological Context
Goethite is a common secondary mineral formed by the weathering of iron-bearing minerals in various geological environments, including hydrothermal veins and sedimentary deposits. It is a major component of limonite, a mixture of hydrated iron oxides.
