Copper-Tin Veins of the Akénobé District. 



Fig. 5. Nearer view of the Daisen mine (D). Q = Quartzite cliff. 



Schalstein and Diabase. Specimens of an apbanitic dark green 

 rock were collected along the road near the Daidô mine. In the 

 field this was taken for a metamorphosed slate, becanse it was 

 intercalated between highly metamorphosed, more or less epidotized, 

 dark green slates, bnt after a microscopic examination, it was 

 found to be a dial)asic rock, whose original ferromagnesian mineral, 

 augite, is entirely uralitized— m-alite diabase. This rock is evidently 

 ix member of the Paleozoic formation representing a schalstein 

 horizon, as is usual in the Chichibu System. 



Under the microscope, the rock is found to be composed 

 •cliiefly of amphibole and decomposed plagioclase (PI. IL, Fig. 5) ; 

 both constituents are 0.3-0.5 mm. in length and confusedly aggre- 

 gated. Sometimes, however, ophitic and intersertal structures are 

 recognized, the interstices between the lath- shaped plagioclase cry- 

 stals usually being filled with uralitized augite. Plagioclase is as 

 .a rule badly kaolinized and appears cloudy, and the borders are 



