Bituminous argillaceous schists: compact rocks with thin bands or foliation, composed of dark schistose clays, metamorphosed or not, with a high content of bitumen or other hydrocarbons.
Bituminous argillaceous schists
Bituminous argillaceous schists: compact rocks with thin bands or foliation, composed of dark schistose clays, metamorphosed or not, with a high content of bitumen or other hydrocarbons.
IGR (Rivista Italiana di Gemmologia/Italian Gemological Review) è la rivista gemmologica internazionale italiana, nata nel 2016 da Gem-Tech con l’obiettivo di sviluppare in Italia un network informativo per Gemmologi e per professionisti quotidianamente impegnati nel settore delle pietre preziose.
IGR – Rivista Italiana di Gemmologia, the Italian Gemological Review, is the leading International Gemological Magazine in Italy masterminded by Gem-Tech Gemological Institute, a broad information framework for Gemologists as well as professionals involved daily in the gemstone business.
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