Ichikawa — Etched Figures of Japanese Quartz. -163 



is closely connected with atmospheric pressure and temperature 

 concentration of solvent, etc. ; hence it is difficult to reproduce 

 exactly results earlier obtained. 



3. Natural Etched Figures of Japanese Quartz (with PI. V). 



The natural etching of quartz crystals has already been 

 described by Dr. G-. Molengraaff;* in these papers, however, 

 the transformation of the edges has not yet been described in 

 detail. In 1908 I first observed the natural etching of 

 amethyst from Yusenji, Kaga Pro v., with grooves on the 

 edges ; since then I have visited many quartz localities in 

 Japan and collected some interesting new. specimens of natural 

 etching ;f the results of the study of these are illustrated in 

 the following plate : 



Plate V. 



The transformation of the edges and the depression of fig. 

 10, etc., can be observed by the naked eye, but the pits on the 

 crystal faces of other specimens can not be investigated 

 minutely unless under a magnification of 75 to 140 times. 



Fig. 1 shows the natural etching of a left-handed amethyst 

 from Yusenji, Kaga Prov. A is a front view, and the double 

 lines on the edges of the rhombohedron and prism of the 

 crystal show the grooves formed by etching. B is a horizontal 

 projection on a rhombohedral face. C a horizontal projec- 

 tion of the section cut perpendicularly to the vertical axis. 

 Fig. 2 shows the natural etching of a right-handed amethyst 

 from the same locality, A, E, and C corresponding to A, B, 

 and C of fig. 1. Fig. 3 is the natural etching of a Dauphine 

 twin of left-handed amethyst and fig. 4 a similar right-handed 

 twinned amethyst, A, B, and C corresponding to A, B, and C 

 of fig. 1 in each case. 



Fig. 5, A, shows varieties of natural pits on the rhombo- 

 hedron and prism of fig. 1, A, but the pits on the former 

 do not reveal the difference between positive and negative 

 forms. B shows pits on the prism of the same crystal that are 

 very rarely observed, but they do not reveal the direction of 

 rotation. 



Fig. 6 is the natural etching of an amethyst from Ozawa, 

 Iwaki Prov. A is a horizontal projection on the rhombo- 

 hedron of the same crystal, and the double lines on the edges 

 show a new face formed by etching that looks like — ^F. 

 B is a horizontal projection on the section cut perpendicular 



*See Zs. Kr., xiv, 173, 1888; xvii, 137, 1889. 



fSee Jour. Geogr. Tokyo, vol. xv, 235 and 441, 1908; xvi, 129, 1909; 

 xvii, 320. 1910. 



