176 ART. 2. — B. KOTÔ: 



fracture. Microscopically, it is composed of fragments of plagio- 

 clase and ronnd chalcedonic patches, leucoxene-like substance 

 and minute glittering flecks intermixed with amorphous dust. 

 It is " jasperoid " and probably an indurated porphyrite-tuff 

 which is scarcely distinguishable from the indurated tuffite of 

 zone No. 2. 



(c) A grayish-green, compact rock with angular flecks. 

 Microscopically it is seen to be composed of angular crystals of 

 plagioclase imbedded in tlie matrix which is made up of polariz- 

 ing particles together wdth crystals of magnetite and fine grains 

 of epidote. The plagioclase is also epidotized forming clusters 

 with regenerated plagioclase. It is a compact porphyrite-tuff". 



(d) The oft-mentioned green breccia is a fusion-breccia, 

 and not a normal aqueous or seolian tuff". It is usually massive, 

 but sometimes cleaves into the pot- sherd -like flakes characteristic 

 of tufaceous rocks. Microscopically the green splinter is seen to 

 be of pilotaxitic structure with the phenocryst of plagioclase 

 sometimes epidotized, and also the phenocryst of the chloritized 

 ferro-magnesian mineral. The dark splinter is the same volcanic 

 in which magnetite -crystal s are abundantly present. The grayish 

 general mass consists of minute grains displaying aggregate- 

 polarization colours. An unexpected guest is the deeply corrod- 

 ed quartz. 



A) The Ky'ônij-sang Formation in Chj'ôl-la-Do 



Thus far I have spoken of the Kyöng-sang formation exclu- 

 sively as occurring in the province of the same name ; but there 

 are still otlier patches of the same formation in the present area 



