R1: Characterization and description of minerals (Joint Session with The Gemmological Society of Japan)

[R1P-11] Occurrence of zeolites in Tsuo andesite from Nagato City, Yamaguchi Prefecture, Japan

*Mariko Nagashima¹, Miyu Nishioka² (1. Yamaguchi Uni. Sci. Tech. Innov., 2. Yamaguchi Uni. Sci.)

Keywords:Zeolite, Tsuo andesite, Stilbite, Heulandite

Occurrence, assemblages and chemical compositions of zeolite and associated amygdale minerals in Tsuo andesite from Nagato, Yamaguchi, Japan were studied. Amygdale minerals including zeolites were described from bottom and middle andesites, and andesite pebbles from the boundary between middle and upper ones. Stilbite was dominant zeolite in bottom andesite, whereas heulandite and mordenite were common in middle andesite and andesite pebbles. As the results of chemical analysis, zeolites formed in early stage enriched in Ca, and those in later stage enriched in Na and K.