A Study on the Constituent Minerals of Pottery Stones

Abstract

For representative samples of pottery stone from Amakusa, Izushi, Kawaai, and Matsumae, Japan, the constituent minerals were separated by centrifugation using Thoulet's solution, and burning tests, measurements of refractive indices, chemical, thermal, and X-ray analysis were carried out. The variation of the refractive indices of quartz crystals in each sample of pottery stone, if it existed, disappeared almost entirely after the burning at 1300°C. By the X-ray analysis, it was found that the sericites thus separated from Matsumae and Izushi pottery stones, especially the former, are accompanied with some amount of kaolinite, but those from Amakusa pottery stone are accompanied with no minerals; from Kawaai pottery stone a small amount of illite, besides the kaolinite, was found. The differences of these experimental results and the charactristic property of each pottery stone seem to be caused by the presence and quantity of kaolinite and illite, and in addition, by the type of pottery stone deposit.