9i 



little over i million ounces per vein, representing 82 per 

 cent, of the total production. It is difficult to determine 

 the exact number of productive veins owing to the fact 

 that, being very narrow, parts of one vein may be mis- 

 taken for two or more distinct veins. At the present time 

 there are 115 or more productive veins, and the relative 

 productivity of those in the three series of rocks is about 

 the same as it was in 191 1. 



A typical silver-cobalt vein, outcrop on Coniagas, Cobalt. The head 

 of the hammer shows the width. 



ORIGIN OF THi; VEINS. 



After the intrusion of the Nipissing diabase sill. 

 which, on the whole, dips at a low angle from the horizontal, 

 and pentrates both the Cobalt series and the Keewatin. 

 disturbance, probably due chiefly to the contraction of the 

 sill on cooling, caused fissures and joint-like cracks to be 

 formed. These openings were made in the rocks of the 

 hanging-wall of the sill, in those of the foot-wall, and in 

 the sill itself. 



Ore-bearing waters working through or along the zone 

 of weakness produced by the sill deposited their burden in 

 the fissures and cracks. The minerals first to be denositec! 

 were essentially cobalt-nickel arsenides, and related com- 

 pounds, and dolomite or pink spar. The fissures and cracks 



