Limonite is an iron ore, containing a hydrated iron (III)
oxide-hydroxide mixture in different compositions. It is one of the
two major iron ores, the other being hematite – used in the
production of iron.
Limonite is a common iron ore, which forms the coloring matter in
different types of soils. It is usually formed from the chemical
weathering of iron rich minerals, such as biotite, amphibole,
pyroxene, and olivine, the hydration/oxidation of iron rich sulfide
minerals, or from the hydration of magnetite and hematite.