40 ^'«1 XLIIL. Art. 5.— T. Katô : 



The composite nature of the vein and evidence of re-opening 

 of the lissures are well observed at many working places. The 

 diagrammatic sketch of a vein-specimen from a working place in 

 the northwestern part of the Daisen vein, shown in Fig. 9, and 

 that of the exposure at another working place of the same vein 

 shown in Fig. 10 illustrate its composite nature very well. 



On observing the vein at the working places and examining 

 the vein-specimens in the laboratory, we can recognize five succes- 

 sive stages of mineralization in the history of the formation of the 

 vein under consideration, viz., (1) deposition of the main cassiterite 

 ore, (2) deposition of v/olframite-cassiterito ore, (3) deposition of 

 chalcopyrite, (4) deposition of zincblende, (5) deposition of barren 

 quartz, with a little chalcopyrite. 



(1) The Deposition of the Main Cassiterite Ore. 



After the formation of the vein lissures and the brecciation of 

 the wall-rocks along them, the main mineralization took place. By 

 the action of the mineralizing solutions which ascended through 

 the fissures, the wall-rocks as well as the blocks and fragments 

 of the country rock filling the fissures imderwent conspicuous 

 alterations, chiefly silicification. The solutions at this first stage 

 of mineralization were very siliceous. The rock-fragments in the 

 vein occasionally show intense sideritization instead of siHcification, 

 being partially or entirely converted to granular aggregates of 

 siderite. 



The product of tliis stage is the main cassiterite ore consisting 

 chiefly of quartz with abundant cassiterite. The cassiterite is very 

 minute in size, ranging from a microscopic size up to 1 mm. in 

 length, and is irregularly scattered in quartz in the form of grains 

 and ill-defined short prismatic crystals. 



