limonite (lĪmˈənĪt) [key] or brown hematite hĕmˈətĪt, hēˈ–, yellowish to dark brown mineral, a hydrated oxide of iron, FeO(OH)· n H2O, occurring commonly in deposits of secondary origin, i.e., those formed by the alteration of minerals containing iron. Both iron rust and bog iron ore are limonite. It serves as a pigment (see ocher) and as an ore of iron. It is found mainly in Austria and England.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.