Goethite is typically formed under oxidizing conditions as a weathering product of femferous minerals, siderite, pyrite, and magnetite, and is widespread as deposits in bogs. It is commonly associated with hematite, pyrolusite, manganite, calcite, quartz, lepidocrocite, clay minerals, and limonite. Hydrous iron oxide is also called limonite. By x-ray examination, most limonites are actually cryptocrystalline goethite with absorbed or capillary water (Palache, Berman, and Frondel 1944). Several excellent pigment ore sources are found in India. Domestic ochre is mined in Georgia and Virginia.
solid. a-FeOOH, goethite [1310-14-1], has a diaspore structure whose color changes from green-yellow to brown-yellow with increasing particle size.
