Abstract: Calcination of szaibelyite and calcium carbonate mixtures and extraction of magnesium from the calcined products by vacuum aluminothermic reduction were experimentally studied. The effects of calcium carbonate addition， forming pressure and calcination temperature on phases in the calcination products， the burning loss ratio of the mixtures and reduction ratio of magnesium oxide were discussed. The results indicated that most of the MgO were replaced from Mg₃B₂O₆ and Mg₂B₂O₅ by CaO during the calcination process of the mixtures. Moreover， the formation of Ca₁₂Al₁₄O₃₃ favored the reduction of MgO. Although it was favorable for the formation of Ca₃B₂O₆， higher forming pressure caused lower burning loss ratio of the mixture and lower reduction ratio of MgO. The reduction ratio of MgO was greater than 85% when the mixture with m_○Ca/m_○s = 1.9 was formed at 90MPa and then calcinated at 1100°C for 120min.

Key words: reduction, szaibelyite, magnesium, calcium carbonate, aluminum