THE archj!:ax formation of the abukuma plateau. 2«^9 



Where biotite occurs in odIv small quantities, they approach both in 

 appearance and compcjsition to a granuhte. Feldspars, both nionoclinic 

 and triclinic, usually make only a small fraction of the whole rock 

 which, in consequence not infrequent]}^ passes locally into a tv])ical 

 mica-schist. This complex seems to corresj'ond with Harada's Rioké 

 schiefer,'^ so named from the locality of Rioke, Süchi göri, in the 

 province of Tötömi, where the rocks were collected for the first time. 

 Harada seems to have given them that name simply with the pétrogra- 

 phie object of covering with it various schists of his gneiss system, 

 found near the village of Kioké, Vv"ith(3ut assigning to them any s])ecial 

 horizon in his stratigraphie scheme. 



ß) The Upper Takanuki complex embraces multifirious alterna- 

 tions of 1) the titanite-amphibole schists a,n(l i^). the gneiss-mica 

 schists. The first are black, highly crystalline schists with the plane- 

 parallel structure, whose transverse section shows interbanded, thin, 

 light-coloured zones, reciu'ring hundreds of times even in a small cliip. 

 They are perfectly schistose, cleaving easily into papery slabs ; and as 

 tlieir texture is not so compact as that of the underlying mica schists, 

 they readil}^ fall into a bluish-black ashy ])ow(ler on their weatliered 

 surface. These Ijlack, fissile schists are peculiar! v characterized bv the 

 presence of titanite which is found in those forms which resemble rolls 

 of butter (wcclicttförm'uj), and wdth sometimes a black, formless mass in 

 their centre, which is pi'obably of a titaiji ferons iron. Another yery 

 interesting component is the salite which almost exclusively makes up 

 the stuff of the light-green zones. Jiiotite is [)resent, but it never takes 

 an iinportant part in the comp'osition of the rock; still it should l^e con- 

 sidered as a, characteristic ingredient, since it is entirely wanting in 

 the series text aljove it. It may Ije readily recognized on the plane of 

 schisiosity by its gold-yellow, glittering lustre. We name these 



1 Loc. cit. p. 43. 



