124 Ichikawa — Notes on Japanese Minerals. 



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

 matsu Ichikawa. 1 



VIII. Secondary report on the natural Etchings of Calcite 

 Crystals (I and II). 



Natural etchings of calcite crystals from Shimoshinjo, 

 Ecliizen Province, have already been described in this 

 Journal. 2 Since then, I have repeatedly visited this and 

 other calcite localities and collected additional crystals 

 more etched than those before described. These speci- 

 mens are illustrated in the accompanying pages, 125, 127, 

 I and II. The striations formed by etching can be barely 

 observed by the naked eye and the pits, elevations, etc., 

 can only be investigated minutely under a magnification 

 of 75 to 140 diameters. The locality of the specimens is 

 Shimoshinjo, Echizen. 



Fig. 1 (I) shows the etching of a scalenohedral crystal; 

 A is a front view (X5) ; B, a horizontal projection on the 

 vertical axis of A. C, D, E, etc. show varieties of natu- 

 ral pits on the face mR. E is the combination of two 

 pits C and D ; F is more etched than D, the three lateral 

 sides sloping down to the base ; G, H, I, etc. show a group 

 of the C or C, E type of pits, etc. respectively. C some- 

 times shows a curved form as in the external part in G 

 and H ; the angle acb is for C = 140° ; D = 30° ; E and 

 1 = 140°; F = 30°. J, K, L, etc., show varieties of 

 natural pits on the face mR. K is a combination of 

 two individuals of the J type pit. The angles for J 

 are: acb = 80°; dee = 110° ; for L, acb = 80° ; dee 

 = 110° ; adb = 60°. M shows a trigonal pyramidal ele- 

 vation on the face mRn, in horizontal projection. The 

 rhombic plane (abed) with striations is a face of a rhom- 

 bohedron formed by etching; the trigonal plane on the 

 top has a strong luster and is a new face formed by etch- 

 ing. X shows a face (p) of trigonal pyramidal elevation 

 (M), in horizontal position. The angles are : ab'c = 90° ; 

 adc = 70°; bca = 30°. The direction of the isosceles 

 triangle (bca) in the figure is opposite to that of acb in 

 D, but the planes of both the triangles are parallel. 

 Ehombic plates (p) in A, and trigonal plates (t) in B are 



1 For two earlier papers, see this Journal, vol. 42, pp. 111-119, August, 

 1916: vol. 44, pp. 63-68, July, 1917. 

 - Ibid., vol. 42, pp. 113-115, 1916. 



