Goethite on quartz Locality : Wawa, Chabanel Township, Algoma District, Ontario Canada Size : View 1.8cm — Photo: Didier Descouens · CC BY 3.0
Goethite
Also known as: Bog iron, Brown iron ore.
The α-polymorph of iron oxyhydroxide — the rust-colored mineral of soils, bogs and gossans, and a major iron ore.
Intro adapted from Wikipedia (CC BY-SA).
Goethite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula FeO(OH).
It crystallizes in the orthorhombic crystal system (space group Pbnm). It is a member of the Diaspore structural group.
Key properties: Mohs hardness 5–5.5; specific gravity 4.28; typically brown or yellow or black or red; Brownish yellow, yellow-orange, ocher-yellow streak; Imperfect adamantine metallic to dull earthy; silky when fibrous luster; optically biaxial.
IMA symbol Gth, IMA status: approved, named in 1806.
A common weathering product derived from numerous iron-bearing minerals in oxygenated environments; an important component of ore in weathered iron deposits. Also a primary precipitate in hydrothermal, marine.
It is found associated with Lepidocrocite, hematite, pyrite, siderite, pyrolusite, manganite, many other iron- and manganese-bearing species.
The mineral was named to honor the German poet, dramatist, and philosopher, Johann Wolfgang von Goethe (1749–1832).
Collections: Everyday Minerals, Collector Favorites.