MR. T. H. HOLLAND ON ROCK-SPECIMENS FROM KOREA. 175 



granitic rocks, breaking through the crystalline schists in that area, 

 uiid forming the low rounded hills of the district. A specimen taken 

 from Caijtlc Hill, Etimsong, is a medium-grained rock, with a specific 

 gravity of 2-Gl. Under the microscope, we recognize quartz, in 

 granular crystals, biotite, changing into chlorite, orthoclase, con- 

 siderably kaolinized, and plagioclasc, exhibiting examples of crystals 

 with a progressive zonal development from a more basic plagioclase 

 in the centre to the more acid types at the periphery. From its 

 microscopic characters this rock would come under the definition of 

 the (jramtite of Gustave Eose. A closely related rock, but more 

 decomposed, and having a specific gravity of 2-58, occurs near 

 Fusan, Kyiing-sang Do. 



A specimen of pegmatite, found by Mr. W. G. Aston near Soul, 

 is almost devoid of mica, and consists of a decomposed aggregate of 

 flesh-coloured felspar and quartz. The rock might be described as 

 an aplite. Aplite has been described by Prof. Roth * from Tsu- 

 shima, an island off the south-east coast of Korea ; and Capt. Basil 

 Hall describes some specimens from two small islands on the south- 

 west coast, lat. 34^ 23' N., long. 126^ E., as " a decomposing, fine- 

 grained rock with flesh-coloured orthoclase, white quartz, and 

 porcelain clay " t. 



Besides the above -selected localities, granitic rocks are found in 

 various parts of the country breaking through the crystalline schists, 

 and forming, in the southern provinces, the principal factor in the 

 formation of the mountain-peaks and -chains ; one of the highest in 

 the south being Mount Kimousangsan, reaching an altitude of about 

 3000 feet, situated W.S.W. of Sonsan, in west Kyong-sang Do. 

 Mr. Gowland has found rocks of similar type cropping out also at 

 the following places along the line of route : — In Kyong-kwi Do, at 

 Yong-in, about 70 li south of Soul, at Pekkerami, north-west of 

 Chuksan, and at Chuksan ; in Chhung-chhong Do, at Chhung-ju, at 

 Brambe, and at various points over the Mungyong pass to the 

 province of Kyong-sang, where granite occurs at Yuko, 40 li S.S.E. 

 of Mungyong, and thence at intervals to Hamchhang, Sangju, 

 Sonsan, and Haiphyong. At Yangsan it is again exposed, and 

 occurs plentifully along the route from that town to the coast at 

 Fusan. 



The granite is found in all stages of decomposition in the same 

 district. Near Soul, for example, there is to be found a beautiful 

 example of the decomposed rock in which the felspathic constituents 

 have been almost wholly reduced to a powdery mass of kaolin, 

 leaving the unaltered quartz-crystals, and, here and there, a clear 

 plagioclase, whilst cubes of pyrites, of from 2 to 5 millim. edge, have 

 been developed. The rock gives no effervescence with dilute 

 acids. 



Euriies. — Acid eruptive rocks are found varying in crystalline 

 characters from the true granitic type to those presenting the 



* Op. at. p. 876. 



•f Op. cit: Appendix, p. cxxviii, 



N 2 



