Datolite from Somi, Miyazaki Prefecture, Japan

Abstract

Datolite of Somi is white in color and massive, occuring in the druses of metamorphosed rhyolite or dacite of the Miocene Sobosan volcanic rocks.
Optical data are: α=1.630, β=1.657_??_1.659, γ=1.667, 2V=(-)75. Chemical composition and X-ray powder data are shown in table 1 and 2.
It is associated with axinite, epidote, chlorite, grunerite-like amphibole, showing the mode of occurence different from any of the known cases such as limestone contact. Also, genetical problems of datolite from Japan are considered in this paper.