3° 



have been supplied by devious channels between the shifting 

 blocks of country rock. Whether these channels still exist 

 beneath the surface or were above the present level is un- 

 certain. Probably the present surface is thousands of feet 

 below the original one, so that connections from above 

 might have been eroded away. 



The columnar deposits at Copper Cliff and No. 2 mine 

 are not the most extraordinary of their kind, since two still 

 smaller columns have been followed downwards for 1,600 

 feet at Victoria mine. 



The Copper Cliff offset deposits occur in contact with 

 a variety of country rocks such as granitoid gneiss and 

 greenstone among eruptives, and graywacke and pink 

 quartzite of the Sudbury series among sediments, without 

 any change in the character of the ore ; and they are cut by 

 dikes of granite and diabase which have likewise had no 

 appreciable effect in changing the original ores. 



In addition to typical offset deposits where the connection 

 with the basic edge of the nickel eruptive is manifest there 

 is one very important band of gossan and ore which runs 

 nearly parallel to the edge of the norite with no suggestion 

 on the surface of any connection. This is the Frood-Stobie 

 offset north of Sudbury, the largest known body of ore in 

 the district. There must have been subterranean channels 

 through which the pyrrhotite-norite and ore reached their 

 present position in this unique case. The Frood-Stobie 

 offset runs as a narrow gossan covered ridge with one or 

 two interruptions for nearly two miles from southwest to 

 northeast, and touches several types of rock, such as gray- 

 wacke and greenstone, but nowhere comes within three- 

 fourths of a mile of the norite edge. 



Diamond drill cores prove that the deposit dips at first 

 with an angle of 60 degrees or 70 degrees toward the norite, 

 Avhile at a greater depth the inclination flattens decidedly 

 suggesting a broad underground connection with the parent 

 eruptive sheet. 



The Frood-Stobie offset has been proved to contain more 

 than 35,000,000 tons of average ore and far surpasses in 

 magnitude any other known ore body in the Sudbury region. 

 It has already furnished half a million tons of ore and shafts 

 are now being sunk by both the Canadian Copper Company 

 and the Mond Company, so that it will soon add greatly to 

 the quantity mined in the district. 



