20 ART. 12. — B. KOTÔ : 



does the footwall frequently show slicken-sided faces, but also the 

 interspaces of two dissimilar rock types are filled with débris, un- 

 doubtedly derived from faulting. This débris, mainly originating 

 from the rocks of the footwall, also contains ore though of a 

 poorer quality than that of the contact limestone, which fact is 

 clearly shown in the results of analyses (Nos. 4, 5, and 10 are 

 specimens of this type) ^\ The deep yellow staining, generally 

 visible in such débris, is evidently not a result of simple weather- 

 ing, and must be attributed to the effect of infusion by some 

 particular process after the filling up of the fault-gaps. 



The western ore-body extends to the south slope of a granitic 

 hill which separates Hol-gol and 3Iorai-chhi. Here for about 120- 

 140 feet to the west of adit No. 23 the western h a 1 f of the 

 stretch is mostly covered with reddish stained earth, the ultimate 

 product of the weathering of porphyritic granite, which was form- 

 erly worked for gold washing ; Avhile the eastern half is 

 chiefly composed of a highly acted and endomorphically altered 

 granitic mass ^^ in which the irregularly impregnated crust of iron- 

 oxide, and wild strings and veins of drusy quartz are intermixed 

 with yellow and red earth. These form the outcrop of the southern 

 limit of the western ore-body (the analyses of No. 7, A, B and 

 C give the results of the sj^ecimens taken from this outcrop), the 

 aspect of which closely resembles what we usually find where hot 

 springs act on the surrounding rock mass (hydatopneumatolytic). 

 The whole stretch seems to be the margin of the granitic stock 

 of On-jin-san, deeply subjected to a pneumatolytic process at a 

 later stage of the plutonic intrusion. 



1) See the heading "Analyses of Ores", p. 27. 



2) It seems to me to be the general rule that the intruding rock is devoid of ore-bodies 

 large enough to be profitably worked. 



