Mineral "Goethite"


Santa Eulalia, Chihuahua, Mexico, private collection from Netherlands.

Goethite is an iron oxyhydroxide containing ferric iron. It is the main component of rust and bog iron ore. It is found in soil and other low-temperature environments such as sediment. Goethite has been well known since ancient times for its use as a pigment (brown ochre). Evidence has been found of its use in paint pigment samples taken from the caves of Lascaux in France. The mineral was named after the German polymath and poet Johann Wolfgang von Goethe (1749–1832).  It is usually a dark, uninteresting mineral, though specimens from a handful of locations are remarkable for their delicate and beautiful crystal growths and velvety botryoidal growths. Goethite is also frequent as black crystal sprays that form within geodes on drusy Quartz. It commonly forms a pseudomorph after other minerals, especially Marcasite, Pyrite, Siderite, and Gypsum. Excellent specimen of lustrous, goethite from Mexico. Great luster. Good botryoidal shape. Age-related wear, fractures and minor cracks may appear. Dirt and dust may exist. Size approx. 6,3cm x 4,8cm x 3,6cm. Weight c. 102g.