Goethite
Chemical Formula	α-FeO(OH)
Species	Oxides & Hydroxides
Crystal System	Orthorhombic
Mohs Scale	5
Specific Gravity	3.3-4.3
Color	Yellowish to reddish to dark brown
Streak	Brown, brownish yellow to orange yellow
Luster	Adamantine, Silky, Metallic, Dull
Refractive Index	n = 2.260 - 2.275 n = 2.393 - 2.409 n = 2.393 - 2.409
Diaphaneity	Opaque
Cleavage	Perfect; less perfect.
Fracture	Irregular/Uneven
Geological Setting：Common weathering product, primary hydrothermal mineral, bog and marine environments.