Copper-Tin Veins of tlie Akénobô District. 11 



As can be observed by a general geological reconnaissance of 

 the Akénobé district, the black slate complex appears to occupy a 

 higher position than the gi'een slate complex, and, moreover, the 

 former is commonly far less metamorphosed and disturbed than 

 the latter. The conglomerate bed, a member of the black slate 

 complex, contains gravels of diverse character, of which flinty 

 hornstone or chert plays an important part ; the flinty hornstone 

 is a characteristic member of the Paleozoic formation of Japan. 

 Tims, although the exact age of the black slate complex remains 

 undetermined, because no leading fossil has been found even in 

 the limestone bed intercalated in it, it is evidently younger than 

 the green slate complex and probably of the Mesozoiç age. 



The predominant rock of the Mesozoic formation in question 

 is black slate. It is highly carbonaceous, and shows distinct 

 cleavage almost parallel to bedding planes. Adjacent to the veins 

 it is frequently more or less silicified or admixed with chlorite, 

 and resembles in some respects the wall-rock of the Daisen and 

 other veins in the Paleozoic terrane. In places, it is intricately 

 traversed by quartz veinlets. 



Gray-coloured shale, poor in carbonaceous matter, occurs fre- 

 quently as a thick bed intercalated between the black slates. 

 Sandy shales, representing all gradations between shale and sand- 

 stone, are likewise common associates. 



Sandstone is also intercalated between slates, sometimes as a 

 thick bed. When fresh, it is gray in colour and compact in 

 texture, but when altered, particularly by the minerahzing solutions, 

 it has become more or less green in colour and is easily mistaken 

 for a diabase. 



A conglomerate bed is exposed on the upper course of the 

 valley along wdiich the Daijuko mine lies. The same bed is- 



