Mineral Species: Goethite

Chemical Formula: FeO(OH)

Chemical Name: Hydrous Iron Oxide

Mineral Class: Oxide

Mineral Notes: Goethite is named afer the German poet, Johann von Goethe. It is a major constituent of rust and an important source of iron. Goethite is created by the absorbtion of oxygen by Pyrite and other iron bearing ores. It is also the main constituent of Limonite, which is a generic name for a variety of mixed iron oxides. There are several polymorphs of FeO(OH), including Feroxyhite and Lepidocrocite, which means they have the same composition but different crystal structures.

Description: A heavy specimen of red-black Goethite showing several highly crystalline zones. At least two different habits are present including prismatic and tabular, although magnification is needed to distinguish between the two. The specimen also contsins an appreciable amount of Hematite, as well as possibly other forms of iron oxide.

Location: Great Perran Iron Lode, Holywell, Cornwall, England.