Goethite hydrous iron oxide crystals
Goethite was often found in the cavities of limonite and taken for one of its varieties. In 1806 it was identified as a separate mineral, and named goethite in honour of the great German poet and dramatist Goethe (1749-1832), who was also a collector of minerals. In colour and chemical composition it resembles limonite. However, in contrast to limonite, it forms small crystals which are usually fine and needle-shaped. The rusty brown colour and velvety smoothness of the crystals are typical of the ‘velvet variety’ found in Pribram (Czech Republic). Goethite occurs with limonite through the weathering of pyrite, or may be formed from hot solutions (hydrothermal origin), or by dehydration of limonite. The most noted deposits are in Sieger-land (Germany) and in Cornwall (UK). In the Slovakian Erzgebirge (Ore Mountains) it is mined as an iron ore from deposits in which it is present in larger quantities simultaneously with limonite. Economically it is of little value. Large pseudomorphs after pyrite are found at Pelican Point near Great Salt Lake in Utah (USA).