Ichikawa — Notes on Japanese Minerals. 131 



same as figure 6, but shows both pits and elevations on 

 the face. A and b are trigonal pits ; c a trigonal ele- 

 vation. Figures 8 and 9 show repeated twin on o, 

 Figure 10 shows a penetration- twin of two tetrahedral 

 crystals in horizontal projection. Figure 11 shows pits 

 of a penetration twin that is in the same position as 

 figure 10. 



A shows a face of the tetrahedron cut to dodecahedron 

 by extension of the dodecahedron accompanied by each 

 individual in the twin, a% hexagonal pit ; b% trigonal pit ; 

 (f, trigonal elevation. The summit angle of the V-shaped 

 pits on the dodecahedral face is 75 °, and their walls are 

 parallel to one of the alternate large walls (t) of the hex- 

 agonal pits on the dodecahedral plane. Striations on the 

 sides of b, d, f, h, j, I, etc. are parallel to one edge of the 

 V-shaped pits adjoining the dodecahedron; therefore, it 

 is proved that V-shaped pits and striations on alternate 

 external sides of the dodecahedral plane are formed by 

 development of a part of hexagonal pits on internal sur- 

 face of the plane. B, is a reversed form of figure A 

 (compare figure 10). C shows the union of two dodeca- 

 hedrons in a lateral face (i, j, k) of figure B, in horizontal 

 position. 



The above study shows that hexagonal pits are only 

 observed on the face of the plus tetrahedron, and trigonal 

 pits, elevations, etc. are found on the faces of both tetra- 

 hedrons (refer to figures 7 and 11, A). , 



Kitashinjo-irmra. Imatate-gun, Fukui-ken, 

 Japan, May, 1918. 



