Chlorite in so-called propylite near the Budô Mine, Niigate Prefecture

Abstract

The mineralogical properties of chlorite of so-called propylite near the Budô Mine, Niigata Prefecture are given and discussed. The chlorite is pale green fine flakes with low double refraction and weak pleochroism of X: pale green, Z: green, and occurs replacing mafic minerals and filling up amygdales, which are filled by aggregates of relatively large flakes of the chlorite. The chemical analysis of a specimen of the chlorite accumulated from amygdales agrees with that of ripidolite. The structural formula is written:
(Mg_19·6 Fe''._15·5 Fe'''_1·5 Al_11·4)(Si_21·2 Al_10·8) O₈₀ (OH)₆₄
The ferric iron is considered to be an oxidized state of the ferrous iron in the octahedral layer. The X-ray powder pattern was examined.