用天然二水石膏单晶进体行了脱水制备半水石膏的试验 ,分别制备了 α半水石膏和 β半水石膏。对其形貌特征进行了扫描电子显微镜观察 ,发现它们的形貌特征有很大的差异。结合其 X射线衍射图谱 ,分析了它们的形成机理。指出造成 β半水石膏经可溶性硬石膏向不溶性硬石膏转变温度比 α半水石膏高的原因是由于其结晶程度比前者差 ,而结晶程度与其形成机理有关 With natural dihydrate gypsum single crystal into the body of dehydration preparation of hemihydrate gypsum test were prepared α hemihydrate gypsum and β hemihydrate gypsum. The morphological features were observed by scanning electron microscopy and found that their morphological characteristics are very different. Combined with their X-ray diffraction patterns, their formation mechanism was analyzed. It is pointed out that the reason of β-hemihydrate transition from soluble anhydrite to insoluble anhydrite is higher than that of α-hemihydrate gypsum is due to its poor crystallinity compared with the former, and the degree of crystallization is related to its formation mechanism