Feroxyhyte
A brown magnetic iron oxyhydroxide forming rounded concretionary masses.
Intro adapted from Wikipedia (CC BY-SA).
Feroxyhyte is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Fe³⁺O(OH).
It crystallizes in the hexagonal crystal system (space group P-3m1). It is a member of the Feroxyhyte structural group.
Key properties: specific gravity 4.2; optically uniaxial.
IMA symbol Fox, IMA status: approved, named in 1975.
Found in sea-floor Fe–Mn concretions. As cement and coatings on clasts in chemically reduced, poorly drained soils and sediments, formed by the rapid oxidation of ferrous compounds.
It is found associated with Lepidocrocite, goethite.
The name refers to the principal components, iron (FERrum), OXYgen, and HYdroxyl, in its composition.