OX THE PIEDMONT1TE-EHYOLITE FROM SHINANO. ^21 



with those of the deep purple specimens from other localities, a 

 difference due to the less amount of manganese present. 



In convergent polarised light, the basal plane shows only one set 

 of interference rings, inside fringed with red, outside with violet. 

 The difference of dispersion of the two rays could not be measured 

 because no plane containing the two poles was obtainable. 



Common epidote also occurs in this rock, as I have mentioned 

 before, and even in a crystal -aggregation the co-existence of the 

 common and the manganese epidote is not rare. Fig. 4 shows 

 an example of such a case. The mineral there figured was once 

 feldspar, most probably, as may be conjectured from the outline of the 

 pre-existing crystal, but no trace of the feldspar remains. Radiating 

 needles of epidote, of characteristic olive-greeu colour, are at the right 

 and left corners of the figure, and the light-rosy piedmontite in the 

 centre. The transition from one to the other, however, is very 

 gradual, showing how a small supply of manganese to the epidote has 

 produced the piedmontite. 



Both epidotes form a peculiar zonal stracture. The two minerals 

 are alternately developed in the direction of the fr-axis, as shown in 

 Fig. 5, but not in concentric zones, so common in the glaucophane- 

 schist of Otaki-san, described by B. Koto.* Basal section of these 

 crystals shows, as seen from the figure, a beautiful rosy-red pied- 

 montite zone in zigzag bands, parallel to the well-developed prismatic 

 faces, and then succeeded by light-yellow common epidote in the 

 direction of the 6-axis. This fact indicates that these crystals have 

 grown laterally, and that the zones with slightly but distinctly dif- 

 ferent chemical composition were formed layer by laver on the ends 

 of the crystals. 



* B. Kotô, op. cit. 



