S. Tahikawa — Some Notes on Japanese Minerals. 113 



II. Natural Etching of Calcite Crystals. 



The natural etching of Japanese calcite crystals has already 

 been described by Prof. K. Jim bo and Mr. F. Otsnki, but the 

 etched figures on other faces (except mR, -mR, etc.) and the 

 forms resulting from the etching have not yet been described 

 in detail. In 1907 I observed calcite crystals in Tertiary tuff 

 from Shimoshijo, Shinyokoe-mura, Imatate-gun, Fukni-ken. 

 Since then, I have repeatedly visited the same locality and 

 collected additional crystals more etched than those before 

 described. These specimens are illustrated in the accompany- 

 ing figures 1 to 7 (II). 



Fig. 1, A, shows a short prismatic crystal (— J/jJ, -mR, ooR, 

 mRn, <xP2, etc.) with natural etchings. B shows the rhom- 

 bohedral elevations that are observed on the face — |i?, in hori- 

 zontal projection ; here the pole-edges of the rhombohedral 

 elevations are parallel with striatums on the face -%R. C shows 

 two elevations accompanied by rhombohedral elevations which 

 are rarely found. D shows the relation between the outlines 

 of the pit, striations, etc., and the edges of the faces ooR. In 

 the striations the angle BAC is nearly 140°. In the pits 

 the angles are : AOB = 120° ; BOC = 28° ; COD = 45° ; 

 DOE = 90°. E and F show a group of the pits on the faces 

 of ooR. The outlines of the figures A and B are magnified six 

 times, but the pits themselves are magnified 80 to 140 times. 



Fig. 2, A, is a long prismatic crystal with the same faces as 

 fig. 1, A. B is a horizontal projection on the vertical axis of 

 the crystal. The outline of the figure is magnified 7 times, 

 but the pits 80 times. 



Fig. 3 shows various forms of natural pits on the faces -mR, 

 <x>R, etc., of the above crystals. On the face -mR, A and C 

 are observed abundantly, but B is very rare. On the faces 

 of oo R, D, E, and F are observed abundantly, but G and J 

 are very rare, the angles are : E(ABC) =.90° ; F(ABC)=110°; 

 G(ABC) = 80°; J(ABC) = 100°. On the face X{mRn\\ 

 H and I are observed. On the faces — \R, <x>P2, mPn, etc., 

 striations are usually observed. The outline of the figure is 

 magnified 10 times, but the pits are magnified 80 to 140 times. 



Fig. 4 shows natural pits formed on the rhombohedral faces 

 {mR) of a prismatic crystal. A is a front view. B is a hori- 

 zontal projection on the vertical axis. C and D show pits on 

 the rhombohedral face in horizontal position ; the angles are : 

 ABC = 80° ; ADC = 40°. 



Fig. 5 shows natural pits and striations formed on a face of 

 co P2 (magnified 360 times). 



Fig. 6 shows natural etchings on the solid angles between R 

 and co R. The figure is magnified 9 times, the etched figures 

 140 times (angle A = 30). 



