In the present investigation,the principal phases in alunite rock from Ping-Yang and Lu-Kiang have been studied.They were α-quartz,hematite and alunite.The latter was a mixed crystal of the type (K,Na)Al₃(SO₄)₂=(OH)₆.In alunite rock,α-quartz and hematite were embeded in the alunite phase.In order to elucidate the nature of the alunite phase in alunite rock,the lattice constants and structural parameters of sodium alunite were determined and compared with those of potassium alunite.