6 9 



occurrence of this metal in veinlets which penetrate granite 

 boulders in the Cobalt series, in the vicinity of the veins at 

 the Coniagas and Trethewey mines. Certain dikes from 

 the granite penetrate the Keewatin in the lower workings of 

 the Temiskaming mine and are cut through by the vein. 

 The granite is here coated with silver. 



In the township of Lorrain, to the east of Cobalt, much 

 of the granite presents a weathered surface, there being a 

 gradual transition from the undecomposed rock to the over- 

 lving sediments of the Cobalt series. 



THE COBALT SERIES 



The age relations of this series of fragmental rocks are 

 shown in the table on a preceding page. 



Since eighty per cent, or more of the ore mined at 

 Cobalt has come from veins, or parts of veins, that are 

 found in this series, it is the most important, from an 

 economic point of view, of the rock groups of the area. 

 Hence the name given to it is appropriate. The series also 

 presents many other interesting features. 



Erosion has left but remnants of this series, which in a 

 past age covered practically all the surface in a vast region 

 in Northern Ontario. 



The series is wholly of fragmental origin, and contains 

 rocks varying from those that are uniformly fine in grain to 

 those that contain boulders several feet in diameter. The 

 kinds of fragments composing these rocks are almost in- 

 numerable, representing as they do the erosive products 

 from all the older pre-Cambrian series of the region — ■ 

 Keewatin, Laurentian, Temiskaming, Lorrain granite and 

 intrusives of various ages. Naturally, fragments of the 

 harder rocks and minerals have withstood better the des- 

 tructive agencies to which thev have been subjected, and 

 the Cobalt series, especially the members of it that are 

 coarser in grain, contain grains of feldspar and quartz, and 

 pebbles and boulders of granite and other igneous repre- 

 sentatives, in greater numbers than they do of minerals or 

 rocks that weather or are abraded more readily- But 

 representatives, as has already been said, of all the older 

 rocks in the region are to be found in the form of pebbles 

 or boulders as components of the Cobalt series. 



