1. Department of Crystallography, Geological Faculty, St. Petersburg State University, Universitetskaya Nab. 7/9, 199034 St. Petersburg, Russia
2. Nanomaterials Research Center, Kola Science Center, Russian Academy of Sciences, 184200 Apatity, Murmansk Reg., Russia
3. Institute for Material Science, Synthesis and Real Structure, University Kiel, Kaiserstrasse 2, 24143 Kiel, Germany
4. Institute for Geosciences, University Kiel, Olshausenstrasse 40, 24118 Kiel, Germany