In order to establish the adequate calcination temperature to obtain Cao, the sea sand sample was analyzed by DSC/TGA. The TGA curve of the sea sand is presented in Fig. 1. As can be seen, the sample lost weight in three steps. The first step at around 110 C is due to the loss of physically adsorbed water from the sur- face of the porous sample. The second step, at around 400 C, can be attributed to the change of aragonite to calcite. This result is in agreement with that reported by Yoshioka and Kitano 1211. who reported the change of these polymorphs at 380-470 eC. The third step observed at 670 oc is due to the decomposition of the remained CaCO3.