THE ARCH^AN FORMATION OF THE ABUKUMA PLATEAU. 271 



Gozaisho complex, we find a quartzose rock of an uninviting, dirty- 

 greyish appearance with a characteristic vitreous histre on its 

 fractured surface. Looked at from the side it seen to be formed of 

 fine banded, sKghtly rosy, garnetiferous stratulie alternating with 

 other greyish ones. Under the microscope it is seen to be mainly 

 made up of quartz, garnet, and chloritoid, severally traversed by 

 veinules of quartz. The garnet dodecahedra are plentiful, the rosy 

 zone being especially so mottled by aggregates of this mineral 

 as to make the section appear dull. The colour of the garnet is 

 fiintly red ; small crystals of it are, however, colourless. 



The chloritoid occurs in lamellar masses with irregular outlines 

 and also in rounded forms. The latter are of plum-green shade, non- 

 pleochroic, and indifierent to the action of polarized light ; sections 

 of the former exhibit a few cleavage lines from which the direction 

 of extinction deviates at an angle of about 15.° The pleochroism is 

 distinctly pronounced, the rays vibrating in the direction of the 

 principal axis are plum-green, those at right angles to it, olive- 

 yellow. The thick, brittle, lamellar mass of this mineral has a 

 tendency to aggregate at certain spots, and the crystals of garnet 

 are here particularly abundant. The characters of our chloritoid agree 

 well in essential p(3ints (Photogramme 1, PI. XXVI) with those of the 

 Austrian occurrence whose description has been given by v. Foullon^ 

 This rock is found at Naka-Misaka, near a water-mill, Iwamae göri. 

 Another rock belonging to the same category was taken from near the 

 temple of Gozaisho. 



D. AmiyJiihole-Picrite. 

 The olivine rocks seem to be of a wide distribution within the 



1 Ueber die petrographische Beschaffenheit der krystallinischen Schiefer, etc. Jahrbuch d. geol. 

 Reichsanstalt, 1883, p. 220. 



