[M-ZZ42] Geology and culture

[MZZ42-P03] The Miharaishi slate for the Tosa-suzuri inkstone in Mihara Village, Kochi Prefecture, southwest Japan

*Go-Ichiro Uramoto¹, Riko Nakamura¹, Kota Asayama¹, Kazuya Iki², Maya Adachi², Osamu Tadai³, Yohei Hamada⁴, Wataru Tanikawa⁴, Takehiro Hirose⁴ (1.Kochi University, 2.Cooperative for the Mihara-suzuri Inkstone, 3.Marine Works Japan, 4.JAMSTEC)

Keywords:Miharaishi slate, Tosa-suzuri inkstone, Shimanto Belt

The Tosa-suzuri inkstone, one of the traditional crafts in Kochi Prefecture, SW Japan, has been produced in Mihara Village using black slates called Miharaishi that occurred in the Shimanto Belt. It has been considered that the slate-bearing sequence is the “Cretaceous”, and Miharaishi has a fine texture that is suitable to make grinding surface inkstick and harbors “special Copper powder” called golden stars which constitutes a beautiful view in the inkstone. However, the geological features of the Miharaishi are not well-documented due to the lack of scientific investigation. This study conducted a literature survey and revealed that the slate-bearing sequence is the Eocene Kurusuno Formation. Also, X-ray diffraction analysis of the Miharaishi confirmed the main component mineral of the slate is muscovite, quartz, plagioclase, and chlorite. The metallic mineral in the slate is identified mainly as pyrite which is the origin of golden stars. The grain size of the component minerals in the Miharaishi is mainly fine silt and the surface of the Tosa-suzuri inkstone has fine protruded structures with several micrometers in width and height. The geological features of the Tosa-suzuri inkstone are similar to the inkstone products in other areas of Japan and China, which can be made into high-quality inkstone.