95 



and other metals go into solution. Hence, it is not sur- 

 prising to find in the Cobalt veins minerals or compounds 

 of the baser metals that appear to have been deposited 

 during the later period of vein filling. 



FORMER VERTICAL EXTENSION OE VEINS. 



Certain writers have expressed the opinion that veins of 

 the Cobalt area, that outcrop at the surface or occur im- 

 mediately below the drift covering, represent the narrower, 

 lower parts of wider veins that extended to or towards the 

 original surface. There is no justification for the holding 

 of such an opinion. The few veins that have been worked 

 to a depth of a few hundred feet in rock of one series give 

 no indication of becoming narrower below, although, when 

 the veins are in the foot wall of the sill, the ore tends to 

 become less rich as the vertical distance below the sill or 

 the eroded part of it becomes greater. Moreover, "blind" 

 veins, or those which do not reach the present surface of 

 the rock, have been found. These veins have the same 

 character, as regards width and mineral content, as those 

 which are exposed at the surface. 



Briefly, it appears that after the intrusion of the diabase, 

 fissures and cracks were formed in the rocks of the hanging 

 wall and in those of its foot-wall, and in the sill itself. The 

 openings in the upper wall probably extended a considerable 

 distance upward beyond the sill, but there is no evidence 

 that they reached the surface or that they were wider in 

 the parts that have been eroded. 



Some of these fissures in the upper wall extended down- 

 ward into the sill itself, e.g.. veins on the Temiskaming, 

 Beaver, and Nova Scotia. The veins on these properties, 

 worked at the surface in the Keewatin hanging-wall, and in 

 the diabase sill below, are the deepest mines in the area. 

 No foot-wall vein has been found to be nroductive to such 

 a depth. 



Then there are veins, e.g., that on the Cobalt Central 

 property, which have been worked at the surface in the 

 diabase and followed downward into conglomerate and 

 greywacke which at times lie beneath the sill. 



Again, blind veins are found in the Cobalt series and in 

 the Keewatin where the sill has been eroded. 



