250 K. JiMBö : 



on oP, very deep depressions with curvilinear, six or eight- 

 sided pits elongated parallel to the h axis. The same crystal 

 is etched on the face / with oblong hillocks, pointed down- 

 wards. This specimen is, moreover, etched on other faces and 

 edges. 



Another crystal from Mino, with a brownish colour at the 

 ends of a axis and a bluish along Z», is etched on the face / 

 with oblong depressions which are broader on the upper end 

 and sharp-pointed on the lower. The faces u and o carry 

 irregular nearly horizontal grooves. The d is similarly grooved 

 vertically, and c is roughened with small pyramidal eleva- 

 tions. 



The above mentioned parallel depressions on / are some- 

 times deep and elongated by their union, thus causing a striated 

 apparance of the face. 



One large crystal from Mino is strongly corroded and 

 show numerous projecting pyramidal eminences on the quite 

 irregular upper and lower faces of the individual. This speci- 

 men shows the peculiar colouration mentioned in p. 249. 



The chagrination of the basal face of a brown crystal from 

 Omi, which is without lustre on this jDarticular face, represents 

 in miniature the above mentioned pyramids. That these are 

 due to etching action and not to the arrangement of sub- 

 individuals, is shown by some specimens in which the etching 

 figures on /, u, &c., are in some way connected with the 

 depressions between the pyramidal prominences, which are quite 

 frequently observed on the topaz from Omi. 



Takimoto has prepared numerous cleavage pieces of the 

 smaller Mino crystals (below 1 cm. in sectional diameter) 

 and found beautiful and complicated optical anomalies, which 



