ON THE PERTHITIC STRUCTURE OF MOONSTONES (I)
A MOONSTONE HAVING A NEW TYPE OF PERTHITIC STRUCTURE
1969 年 6 巻 1-2 号 p. 7-16
詳細
1969 年 6 巻 1-2 号 p. 7-16
Since 1921, Kozu, Endo, Hadding, Ito, and Chao and Taylor had investigated into the interlamination of constituent feldspars of moonstone by X-ray methods. It seems however that the problem of the modes of interlamination still defies satisfactory solution. The writers have discovered that moonstones from granitic pegmatites in Shiga Prefecture, Japan, have a new type of inter-lamination of four constituent feldspars. Of these feldspars, one is monoclinic potassium-rich and the remaining three triclinic sodium-rich, two of which are twinned after the albite law. All the (010) planes of the four constituent feldspars are parallel and all the c-axes of the three sodium-rich feldspars are identical in length, parallel in direction, and make an angle of 32′ to the c-axis of the potassium-rich one towards the a-axis of the latter.
This result shows that the interlamination of moonstones does not belong to one limited type, but is classified into such types as discovered by Ito, Taylor and the present writers.
