We obtain a large quantity of precise data by using modern equipments in the second period of the advancement of science. In the third period, we set up a new theory and are awaked in our interest in making new fields of study. Mineralogy in Japan now comes to the third period. In this point ambitious young mineralogists can hope for the future development of mineralogy. We should put emphasis on the study field which develops the different conception from that of physists and chemists. One of such fields is to study the mineral behaviour in the multi-compo-nent systems over an extremely long time and a wide space.
