S. Ichikawa — Some Notes on Japanese Minerals. Ill 



Art. XII. — Some Notes on Japanese Minerals; by Shim- 

 matsu Ichikawa. 



I. Natural Etching of Galena Crystals. 



Galena crystals with rounded edges from Kuratani, Kaga 

 Province, have been long known. Their rounded' edges, how- 

 ever, have not yet been discussed in detail. In 1908 I also 

 observed galena crystals with rounded edges from the Kamioka 

 mine in Hida Province. The natural etching of galena crystals 

 from the above localities is illustrated in the figures of the 

 following plate (I). 



Fig. 1 shows the natural etching of a galena crystal from 

 Kuratani. The pits and elevations are given in detail in figs. 

 2 to 6. 



Fig. 2 shows varieties of natural pits on an octahedral face, 

 the three walls of the pit being parallel to the cubic faces. 

 Fig. 3 shows pits on a cubic face, the sides being parallel to 

 the octahedral faces. Fig. 4 shows natural elevations on a 

 cubic face ; the sides of these elevations are formed by the 

 faces of an octahedron. Fig. 5 shows the relation between the 

 outlines of the natural pits and the edges of the cubic faces. 

 Fig. 6 gives the relation between pits and the cubic cleavage ; 

 the dotted lines of ab, cd, etc., are innumerable pits in the 

 direction of the cleavage. 



Fig. 7 shows the natural etching of a galena crystal, from 

 the Kamioka mine ; details are given in figs. 8 and 9. 



In fig. 8 the pits and striations on the cubic and octahedron 

 are shown much magnified. Fig. 9 shows the relation between 

 outlines of the different pits and the edges of the octahedron. 



Fig. 10 is a cubic crystal with rounded edges, also from the 

 Kamioka mine. The etchings observed on a rounded solid 

 angle are given in fig. 11 (compare fig. 4). 



Fig. 12 shows the etchings on a rounded edge of a cubic 

 crystal ; and fig. 13 the various forms of natural pits on the 

 rounded-edges of a similar crystal. Both of these are also 

 from the Kamioka mine. 



The symmetry of the etched figures on the above crystal 

 faces corresponds to the symmetry of the group to which the 

 given crystal belongs, and the resulting form in the etching is 

 supposed to make up an octahedron (see figs. 4 and 11). 



Fig. 1 is maguified 3 times ; fig. 7, 1*5 times ; fig. 10, 2 

 times ; the other figures from 80 to 140 times. 



Reference should also be made to Becker's results on galena 

 crystals published in 1885. (Min. petr. Mitt., vi, 237.) 



