1. Department of Geology and Mineralogy University of Cologne Zülpicher Str. 49b 50674 Köln Germany
2. Department of Mineralogy Natural History Museum Cromwell Road London SW7 5BD UK
3. CRPG CNRS Université de Lorraine UMR 7358 Vandoeuvre‐lès‐Nancy 54501 France
4. Institute of Geoscience University of Bonn Meckenheimer Allee 169 53111 Bonn Germany