﻿Some Ores and Rocks of Southern Slocan. 301 



their richness in silver. Though in nature and structure 

 they appear quite common, the veins of this class show 

 evidence of a replacement of the granite country rock by 

 ore. These veins, or ore bodies, are nearly perpendicular. 

 The replacement seems to have taken place along a 

 line of decomposed granite, often along two parallel 

 seams, which give the impression of being the walls of 

 a vein. 



The intervening granite is penetrated by ramifying 

 stringers of quartz and patches of galena and zinc blende. 

 In some cases the galena is exceptionally high grade 

 in silver. When this is the case, argentite is probably 

 present along the cleavages of the galena. At other 

 times the galena is low grade, far below the general 

 average of Slocan galenas, which is somewhat over 100 

 oz. per ton. The blende is low grade. A case of dyke 

 interference also occurs with one of these ore bodies. 

 This is a narrow band of rock very similar to the one 

 described before, only of a darker color. Under the 

 microscope it shows itself to be a much decomposed basic 

 " mica trap" allied to the minettes. 



Such dykes, together with others rich in hornblende, 

 are common in all this district. 



An assay of rock from this dyke gave 4 oz. silver to the 

 ton. This may have been accidental, being from an 

 exposure in a tunnel. An analysis gives : — 



SiO^ 39-38 



CaO 13-44 



AlA 22-94 



FeA 11-33 



MgO 9-93 



K^O Notdet. 



Na^O '' 



Total 97-02 



On passing through this dyke, which cuts the ore body 



