Notes on the Topaz from Mino, 



By 

 Tadasu Hiki, Rigakushi. 



College of Science, Imperial University. 



With PI. V. 



Occurrence. — In the northern part of the district Ena-göri, Pro- 

 vince Mino (Central Japan), there is an outlier of a great granitic 

 massif of the Kiso range. The well-known Kiso river, which drains 

 this range, comes from the province of Shinano, and flows through 

 western Mino with broad alluvial plains on both sides. In the eastern 

 portion of the district, that is, on the northern side of the river, stream 

 tin is worked at present within the area of about four square kilo- 

 meters. Many tributaries of the Kiso join here with the main stream, 

 among them the Tengawa, the Chibaragawa and the Kizumizawagawa 

 are worth mentioning. The latter two are rich in topaz and other 

 minerals. Naegi, Takayama, Hirugawa, and Ichinose are also tolera- 

 bly well-known for the occurrence of topaz in this tin-field. 



Most of the crystals of topaz, which will be here described, are 

 from these localities. The district in question is hilly and the whole 

 mass of granitic elevations is surrounded by quartz-porphyry. Loose 

 topaz may be easily collected from the surface soil in the regions of 

 granite and quartz-porphyry ; or from the plusiatic deposit, exclusive- 

 ly derived from these rocks. Besides, they are also found in small 

 rivulets and marshes, and in cultivated soil, associated with cassiterite. 

 The faces of the crystals are roughened by friction and their edges 



