182 



■MR. T. n. HOLLAND ON EOCK- SPECIMENS FROM KOREA. 



of accretion in zones of a decidedly more acid character. Some of 

 the twin-planes of the central, old core are common to the sur- 

 rounding zones, and run the whole length of the compound crystal ; 



Fiff. 3. 



Crystal of porphyritic plagioclnse with a core of older, felspatliic rtiaterifil 

 which bas been scbillerized in four directions and corroded before the 

 ibrmation of the clear zones of a]ess basic character around. In addition 

 to the series of twin-planes running the whole length of the crystal, another 

 set, perhaps older, are limited to the central schillerized core. In andesite 

 from Milyang, Kyong-sang Do. 



Fig. 4. 



Eiagram showing the directions of the planes of schillerization in the above 



(fig. 3). 



hut there are a large number which extend out only to the borders 

 of the Bchillerizcd patch. These latter, perhaps, existed before 

 the formation of the new felspathic material around them. 



