a'HE GREAT ERUPTION OF SAKURA-JIMA IN 1914, 



193 



with the mass. Tho 

 porous portion has mor- 

 tar texture, the round 

 plagioclase (? cordierite) 

 grains I)eing cemented 

 with colorless glass full 

 of vacuoles. Plagio- 

 clase^^-phenocrysts are 

 composed of an aggre- 

 gate apparently forming 

 trillings like those of 

 cordierite, but their 

 mineralogical nature is 

 not yet definitely settled. 

 The writer considers 

 this angular white en- 

 clave (Text-fig. 43) to 

 be petrologically of 

 diopside-gabbro. 



The type — a 

 micronorite (Text- figs. 

 32 and 36). An enclave of noritic composition and motex has 

 been known since the pubhcation of Laceoix's work on Montagne 

 Pelée. In Japan the writer observed the same enclave, of a few 

 centimetres in size, among the effusives of the volcanoes of Ontaké 

 (Prov. Shinano) and Komaga-daké (in Hokkaido). In the ' live ' 

 lavas of Sakura-jima, patches (1 mm.) of noritic segregation are of 



« J) io 



Fig. 43.— White lithoidal microtinite in andesite-ejecta, 

 fonnrl at Yokoyama. 12 x Sohl 



1) Some of the plagioclase now under question may be a cordierite complicately multiple- 

 twinned and penetrated after (110). Some are entirely composed of a cumulative aggregate of 

 colorless rectangular and square-shaped embryo-crystals ^^•ith diagonal extinction. They belong 

 in all f)robability to cordierite. 



