56 Vol. XLIII., Art. 5.— T. Katô : 



showing bright interference colours is fonnd. It is ahnest colour- 

 less or very pale greenish and is distinguishable from chlorite 

 only between crossed niçois. This mineral is most probably 

 muscovite, which has crj^stalhzed chiefly along the selvages. 

 The chlorite crystallized soon after the deposition of muscovite, 

 and filled up all the interstices between the earlier minerals. 



The veinlets under consideration ramify into stringers con- 

 taining (]uartz and sporadic flakes of chlorite, and finally into those 

 consisting exclusively of quartz grains. They are, therefore, con- 

 temporaneous in generation with the quartz veins and veinlets of 

 tlie stage of the main silicification of the country rock. It is 

 further suggested that the stage of the deposition of the main 

 cassiterite-ore corresponds to the stage of silicification. 



Veinlets and stringers of siderite-limonite and siderite- chlorite 

 often cut tlie quartzose veinlets under consideration, though the 

 former have a tendency to be ramified in the latter and to unite 

 to larger veinlets in the silicified and sideritized country rock 

 (PI. Vlh, Fig. 3). 



Pyrite filling the interstices between crystals and grains of 

 quartz is sporadicaUy found in the quartzose veinlets under con- 

 sideration, and is sharply cut by the veinlets of siderite (PI. VII., 

 Fig. 4). 



The country rock, green slate as well as carbonaceous, is 

 extensively traversed, near the veins, by irregularly crossing veinlets 

 of milky quartz, ranging in width up to 2 cm. or more. The 

 quartzose veinlets containing sporadic cassiterite are also intricately 

 cut by these barren quartz veinlets, as can be revealed under the 

 microscope. In the environs of the Daisen and Daijukô vein 

 groups, this phenomenon is most conspicuous. The veinlets of this 

 category are barren, but contain insignificant quantities of bornite. 



