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The changes of physical and chemical properties of sodium pyroxenite gangue such as decomposition and phase transformation were researched by means of differential thermal analysis and X-ray diffraction. The results show that the natural sodium pyroxenite gangue contains the main mineral of aegirite(NaFe+3Si2O6), and it contains a number of BaSO4 and Na3Ca2(SO4)3F, etc. The water of crystallization decomposes at 554.7°C. The Na3Ca2(SO4)3F decomposes into the composite sulfate and CaF2 over a wide range of temperatures. The main mineral of aegirite(NaFe+3Si2O6) reacts with CaF2 into NaF gas at 993.4°C. The sodium pyroxenite gangue is melts and releases a small amount of SiF4 gas in the range of 1193.5-1300.7°C.