Copper-Tin Veins of the Akénobé District. 45 



(2) The Deposition of the Quartzose Wolframite- 

 Cassiterite Ore. 



A qaartzose ore containing abundant wolframite and cassiterite 

 occurs in the form of a vein cutting the composite vein longitudinal- 

 ly, its width varying from a few centimeters to one meter or more. 

 It is most typically developed in the Daisen vein. This ore is tho 

 product of the second stage of mineralization, and cuts the cassiterite- 

 quartz ore, including the ring- ore, of the previous stage, often 

 showing well-defined boundaries (Fig. 9). The writer observed at 

 a working place of the Daisen mine a section of the vein which 

 showed the ring-ore of the first stage in contact with the wolframite- 

 cassitcrite ore of the second stage. The contact was sharply defined, 

 suggesting that the latter was deposited later along a reopened 

 fissure cutting the former. 



The ore in question is practically the same in appearance as 

 the product of the previous stage, except that it contains innumer- 

 able thin plates of wolframite (PI. Y., Fig. 1). Wolframite is 

 characteristically paper-like, commonly with a thickness of less 

 than 0.5 mm.; and confusedly scattered black streaks, representing 

 cross- sections of the wolframite plates, are observed on the fracture- 

 surface of the ore. Along the walls of drusy cavities of the ore 

 cf this stage, small but- beautiful crystals of fluorspar and scheelito 

 are often found. 



In places, specks and patches of native bismuth are found in 

 this ore. This mineral is of rare occurrence in the vein under 

 consideration, and occurs exclusively as a product of the second stage 

 of mineralization. Sometimes, it is found in the form of streaks 

 filling up the cracks along the thin plates of wolframite. Still 

 more rarely, bismuthinite is found embedded in quartz. It is often 

 intimately associated with native bismuth, the latter being enclosed 



