1. Institut für Mineralogie Westfälische Wilhelms‐Universität Münster Corrensstrasse 24 48149 Münster Germany
2. Department of Mineralogy and Petrography Natural History Museum Vienna Burgring 7 1010 Vienna Austria
3. Corning Incorporated, Science and Technology Division 21 Lynn Morse Rd. Painted Post New York 14870 USA