AIM: To explore the machanism of calcined mica by comparing the difference in crystal structure and inorganic elements of raw mica and calcined ones. METHODS: Crystal structures were compared by IR spectrum and X-ray crystallography and the contents of element in the prevention were determined with ICP-AES. RESULTS: After being calcined,crystal phase transformation changed in gold mica and did not change in white mica.Both of their chemical composition changed,crystal water decreased and crystal defects increased.There were obvious differences in the contents of inorganic elements.The content in white mica was obviously more than that in gold mica.After being calcined,the value of K/Na in white mica decreased and the contents of Ca,Mg increased,while the content of Mg increased and the content of Ca decreased in gold mica. CONCLUSION: There are(actually) many differences in contents of elements and chemical structure in white and gold mica before and after being calcined,which may explain the mechanism of calcined mica.