NOTES ON THE MINERALS OF JAPAN. 251 



slightly difiPer from those of Brazilian crystals in Brauns' Optis- 

 chen Anomalien, 1890. 



Ömi. — Ko has described topaz of Tanokamiyama in Omi, 

 which attains as large a size as that from Mino. Small indi- 

 viduals less than 1 cm. in diameter of the basal section are 

 very rarely found, in contrast to their abundance in Mino. The 

 crystalline habit is usually short columnar, while long colum- 

 nar forms, often found in Mino, are exceedingly seldom observed. 

 The colour is mostly l)rownish. Colourless, bluish and greenish 

 crystals are less frequent ; the beautiful light-green colour seen 

 in a specimen of Mino topaz in Wada's collection is found in 

 none from Omi. The following faces have been recognised : — 



oP, P, 2P, œp, œFi, 2Fœ, iFœ, 2P œ ; besides, IP, 2Pr, 



00 PI, 00 Pï, 00 PT, odP ^, iF œ, §P œ. 



Most of the crystals are domatic in termination, but 

 sometimes we find pyramidal or basal endings. 



Enclosures in the Topaz of Ömi are tourmaline, beryl (?) 

 and monazite. The last mineral is found in red-brown crystals 

 with curved faces. The etching figures are essentially like 

 those of Mino specimens ; only the deep octagonal and hexa- 

 gonal pits on c of the latter have not been found. 



A peculiar paragenetic connection of the Omi topaz with a 

 flesh-red coloured potash-felspar is known to collectors. Wada 

 recognises the existence of two generations in the Omi topaz. The 

 younger individuals are smaller in size, usually developed at 

 both ends and richer in faces, than the older generation. 

 They lie on felspars instead of making intergrowth with 

 these. 



Analysis of Omi topaz by Takayama, chemist to the Im- 

 perial Geological Survey : 



