1. Department of Physics and Technology; University of Bergen; Bergen Norway
2. German Gemmological Association; Idar-Oberstein Germany
3. Centre for Gemstone Research, FB 09 Institute for Geosciences; Johannes Gutenberg-University of Mainz; Mainz Germany
4. Department of Physics; Norwegian University of Science and Technology; Trondheim Norway
5. SINTEF Materials and Chemistry; Trondheim Norway