JOUENEYS THROUGH KOREA. 165 



modifications above cited. Tiie color of the rock is also greatly 

 influenced by the quantity of its micaceous components. On 

 account of its coarse texture, the rock easily falls into disintegra- 

 tion creating the waste land which characterizes the scenery of 

 Korea. Corresponding to the macroscopic appearance, the micro- 

 texture presents great diversities, and one never fails to see 

 cataclastic texture, and constrained undulatory extinction in quartz 

 and feldspar, in all the rocks of this group. 



Microcline and quartz are the two predomiuant components of the 

 rock. The latter occurs in the form of granite-quartz which always 

 shows internally constrained, undulatory extinction, and has suffered 

 granulation and smashing from external pressure. The former is most 

 characteristic of our rocks. The microcline '^ occurs in two foims, viz., 

 automorphic megaphenocryst and plate. The {a) plienocryst lias a 

 light grayish-hlue color and prismatic habit elongated toward the a-axis, 

 and attains the extraordinarily large size of 8 cii) -\ . It is ofteii twinned 

 after the Carlsbad laAv. It cannot be distinguished from orthoclase either 

 in its macroscopic or microscopic aspect excepting b}' its reticulated 

 structure, pellucidity and optic orientation, A cleavage x^iece of (001) 

 shows the extinction of 51° with v/m. As the moire structure is 

 frequently observed, so we have here microcliue-micropertliite- 

 The reticulated and perthitic structures are seen in the same plate 

 though the presence oî one precludes that of the other in different 

 parts of the crystal. A modification of the microperthite — a parallel 

 growth of albite and microsline Avitli the b - axis in common, is seen 

 in the Hadong specimen, in which the polysynthetic lamellar albite has 

 a rectangular outline flattened toward the b - axis. 



The (ß) xenomorphic plate of microcline shows also the re- 

 ticulated structure by which character alone it can be distinguished 



1) The Ynk-siiu-nyong specimen (:^ -f- ^), p. 127. 



2) In tlie Ha-dong (^BJ ;^) specimen, p. 40. 



