The Ores and their Associations. 



Referring uow to the nickel and copper ores for which this district is be- 

 coming famous, it may be remarked, in the first place, that there is much 

 uniformity both as to the characters of the ores themselves and the condi- 

 tions under which they occur. Yet these deposits are not confined to the 

 undoubted Huronian rocks, but are equally abundant within the gneiss and 

 quartz-syenite areas. They may be said to be connected with a certain geo- 

 graphical area rather than with a single geological horizon. In other words, 

 it would seem as if, within certain limits, the ores might have had their origin 

 beneath all the rocks found at the surface. The ore consists in all cases of a 

 mixture of chalcopyrite and nickeliferous pyrrhotite. The area over which 

 this ore has been found up to the present time extends from tlie Wallace 

 mine, on Lake Huron, in the vicinity of La Cloche, northeastward to the 

 north side of Lake Wahnapitse, a distance of about seventy miles, and from 

 the southeastern boundary of the Huronian belt, in the Sudbury district, 

 northwestward to the limits of the Geneva lake outlier, a distance of about 

 fifty miles. 



It is rather singular, first, that pyrrhotite should exist so commonly within 

 this region as compared with any other in the country, and, secondly, that 

 no matter in what kind of rock we find it to occur, it should generally be nick- 

 eliferous to an economic extent. Although, as a rule, pyrrhotite, wherever 

 found, contains traces of nickel, it has only been detected in commercial 

 quantities in a few^ places in other parts of the world.* The investigations 

 of the writer in the Sudbury district have shown that the combined nickel 

 and copper ore is found on or near certain lines of contact between diorite, 

 on the one hand, and gneiss or quartz-syenite most frequently on the other, 

 but only at certain points on these lines. As no circumstance is without a 

 cause, we may look for some reason which determines the concentration of 

 the ore at one place more than another, and the writer believes he has found 

 the reason in this case to consist in the intersection of the ore-bearing belts 

 near these occurrences either by one of the diabase dikes above described 

 or else from the pinching in or perhaps from a transverse disturbance of 

 the belt. 



The ore seems to have been derived in all cases from the diorite, but for 

 some reason the proximity of the gneiss or quartz-syenite appears to be 

 also fiivorable for the production of the large deposits. If the diorite 

 flowed out originally upon the nearly horizontal surface of the other 

 rock, the constituents of the ore which it contained may have sought the 



* Assays have recently been nnade of samples of pyrrhotite from near Shreiber and Jackfish bay, 

 Lake Superior, and from the counties of Peterboro', Hastings, and Lanark, in Ontario, none of 

 which yielded more than traces of nickel. 



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