Hydrous sesquioxide of iron, an important ore of iron, occurring in stalactitic, mammillary, or earthy forms, of a dark brown color, and yellowish brown powder. It includes bog iron. Also called brown hematite.
Limonite is an ore consisting in a mixture of hydrated iron(III) oxide-hydroxide of varying composition. The generic formula is frequently written as FeO(OH)Â·nH2O, although this is not entirely accurate as limonite often contains a varying amount of oxide compared to hydroxide.