Glass-Ceramics as Imitation of Gems. II. Optical Spectra, Luminescence, the Nature of the Opalescence of Rare-Earth Glass-Ceramics - V. M. Khomenko; A. N. Tarashchan; V. V. Ripenko; A. A. Vishnevskij; A. A. Kosorukov (Mineralogical journal, 2017)