186 ART. 3. B. KOTO : 



present in the eastern lavas, while in the western it appears only 

 sporadically, especially in submarine lavas, where it is associated 

 with amoeboid -shaped iron ore fringed with secondarily formed 

 prismoids of hypersthene (Text-fig. 40). Pyroxenes are present in 

 variable quantities on both sides, of which hypersthene decidedly 

 prevails over augite in the east, while in the west both com- 

 ponents appear almost in equal proportions. Parallel growths of 

 pyroxenes are more frequent in the east. Plagioclase, being always 

 zonal- structured, occurs very fi-equently in the east in segregation- 

 patches in the form of either micronorite (plagioclase-hypersthene 

 motex. Text-fig. 36)'^ or microtinite (pure anorthite aggregate)."^ 

 Generally speaking, these enclaves of earlier segregation are 

 characteristic to the ' live ' lavas of Sakura-jima. Magnetite occurs 

 in larger clumps in the east, as compared with its idiomorphic 

 development in the west. 



Geoundmass. — All are hyalopilitic ; the glass base being either 

 brownish or colorless in the east, while the latter prevails in the 

 west. The relative proportion of glass, augite microhtes and 

 feldspar laths vary according to circumstances, on which entirely 

 depend the lustre and shades of the color of the lava. 



Augite microlites appear in two modifications, one being clear 

 and euhedral, the other corroded and sprinkled with dust of 

 magnetite. The second type is more frequently met with in the 

 glass-rich variety mingled with only a few feldspar laths. Glassy 

 rocks are abundant in the west. The brown glassy form of ex- 

 ceptional type is also met with in the west, which shows damascened 

 texture, caused by complicated kneading of fl.attened air-pores and 

 dust streams of magnetite (PL XIX. Fig. 5 ; PI. XXIII. Fig. 4), 



1) See pp. 19a-194. 



2) See p. 190. 



