Chepushtanova ? Vasilevskaya T.A. monograph is dedicated to the urgent problem ? pyrite bearing materials treatment. The specification of theoretical aspects of pyrite thermal decomposition with forming of nonstoichmetric pyrrhotites allow to decide the urgent problem ? the involving of refractory pyrite, arsenopyrite and chalcopyrite bearing raw materials to industry. The establishing theoretical results give the opportunity to elaborate the technology of pyrite bearing materials treatment. This book is meant for mining and metallurgy sector, chemical industry, universities, research institutes, specialized associations in the field of metallurgy. In this book, you can find analysis and processing technologies of pyrite and arsenic-pyrite ores, the analysis of structural and technological properties of synthetic hexagonal pyrrhotite, arseno-pyrite, chalcopyrite. In this book, based on numerous physical and chemical research complex assembled the latest results on the structure of hexagonal pyrrhotite, obtained reference data on heat capacity, phase transitions and many other pyrrhotite characteristics.