28 "^'ol. XLin., Art. 5.— T. KatÖ : 



TJie Cross- Fault of the Da /sen Vein. This is tlic most significant 

 fault for practical purposes in this vein district. It lies to the 

 northeast of the Daisen mine and strikes N. E., consequently all 

 the important veins of the Daisen vein group, striking N. W., are 

 cut at right angles by it (PL I.). The fault is utilized for the 

 oross-cut and the main transportation-level connecting the main 

 levels of the Daisen, Nihonmatsu, Sekiei, Hyakken and Shôtoku 

 veins. It is expressed at the surface as a valley and is indicated 

 by the discontinuance of the outcrops of the veins and rocks. 



IV. THE Veins in General. 



Innumerable veins occur in the district under consideration, 

 and in ancient times, especially in the eras of Daidô (800-809) and 

 Entoku (148ü-141)l), they wore prosperously worked for silver and 

 «copper. About thirty years ago this vein district was included in 

 the concession to the Mitsubishi Mining Company. In the early times 

 of prospecting and mining by the present company, the extracted 

 ores were treated as argentiferous copper ore. But recently it 

 was discovered that the siliceous ore containing abundant thin 

 plates of wolframite, sometimes in association with chalcopyrite, 

 contains also much cassiterite in microscopic crystals and grains, and 

 now as much tin ore as copper ore is produced from this district. 

 In fact, the Akénobé mine is the largest tin mine in this country 

 at the present time.^) 



Veins are occasionally found in the dioritic rocks, but most 

 of them occur in the Paleozoic and Mesozoic terranes, particularly 

 in the green slates. Many veins were once prospected or worked 



1) The recent tin iiroduction of the Akénobé mine has been : — 



1917 377,097 pounds 



1918 312,474 „ 



