Pseudomalachite, Goethite
Cu5(PO4)2(OH)4, α-Fe3+O(OH)
Locality:
Clara Mine, Rankach valley, Oberwolfach, Wolfach, Black Forest, Baden-Württemberg, Germany
Field of View: 1.85 mm
Photo: Michael Förch
Pseudomalachite is a phosphate of copper with hydroxyl, named from the Greek for “false” and “malachite”, because of its similarity in appearance to the carbonate mineral malachite. Both are green coloured secondary minerals found in oxidised zones of copper deposits, often associated with each other.
Goethite is a common mineral and is a frequent matrix material for other more aesthetic minerals. It is usually a dark, uninteresting mineral, though specimens from a handful of locations (especially Colorado) 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.
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