Goethite
Description
A yellow earth mineral primarily composed of iron hydroxide. Goethite was named in 1806 for Johann W. von Goethe, a German mineralogist and poet. It is an important iron ore that occurs naturally as an opaque crystalline material. Goethite has been ground and used as a pigment from the earliest times; it provides the yellow coloring in yellow ocher. Large clumps of goethite have also been carved for small ornamental items. It is mined at several locations such as Czech Republic, Germany (Saxony, Westphalia), England (Cornwall), France (Alsace-Lorraine), South Africa, Russia, Australia, Brazil, and the United States (Colorado, Lake Superior, southern Appalachians).
Synonyms and Related Terms
Yellow ocher; ferric hydroxide: iron hydroxide; hydrated ferric oxide; hydrated iron oxide; lepidocrocite (cubic crytstalline iron hydroxide); Pigment Yellow 43; CI 77492; Goethit (Deut.); Nadeleisenerz (Deut.); Gelber Ocker (Deut.); goethita (Esp.); ocre jaune (Fr.); goethite (Fr.); gkaititis (Gr.); kitrinh ochra (Gr.); ocra gialla (It.); gele oker (Ned.); goethiet (Ned.); goetite (Port.)
Physical and Chemical Properties
- Soluble in mineral acids. Insoluble in water and ethanol.
- Orthorhombic crystals occurring in prisms
- Fibrous structure.
- Perfect cleavage in one direction.
- Fracture = uneven.
- Luster = adamantine to dull.
- Streak = yellow.
| Composition | FeO(OH) |
|---|---|
| Mohs Hardness | 5.0 - 5.5 |
| Density | 4.28 g/ml |
Resources and Citations
- Mineralogy Database: Goethite
- Submitted information: Fred Gamble, October 2007
- Encyclopedia Britannica, http://www.britannica.com Comment: "goethite" [Accessed December 11, 2001]. (BW photo) ..
- C.W.Chesterman, K.E.Lowe, Audubon Society Field Guide to North American Rocks and Minerals, Alfred A. Knopf, New York, 1979
- Wikipedia: http://en.wikipedia.org/wiki/Goethite (Accessed Sept. 7, 2005)
- Jack Odgen, Jewellery of the Ancient World, Rizzoli International Publications Inc., New York City, 1982
- Van Nostrand's Scientific Encyclopedia, Douglas M. Considine (ed.), Van Nostrand Reinhold, New York, 1976
- Random House, Webster's Encyclopedic Unabridged Dictionary of the English Language, Grammercy Book, New York, 1997
- The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998