USEFUL METM 



igm -iiii> n.rks made in the laboratory of the I'liite.l stai.-- 

 ( Jmlogiral Survey an average of 0.0274 per cent . nicki-l <>\i<le was 

 found. The sulphides and the arsenides of nickel may be formed 

 by cither the wet or the dry processes. Where capillary millerite 

 appears on dolomite crystals lining geodes it is unquestionably 

 crystallized from solution. When- it occurs as a radiating in- 

 crustation upon secondary minerals as in Pennsylvania, it too 

 must be of secondary origin (Fig. 119). 



The origin of nickeliferous pyrrhotite is perhaps an open 

 question. According to J. H. L. Vogt it represents a distinct 

 segregation from a molten magma. This has long been con- 



FIG. 119. Evans mine, Canadian Copper Company, Copper Cliflf, Ontario. 

 (After A. E. Barlow, Canadian Geological Survey.) 



sidered the origin of the Sudbury, Ontario, pyrrhotite. The 

 order of segregation has been most carefully studied by R. Bell, 

 H. B. von Foullon, T. L. Walker, A. P. Coleman, A. E. Barlow 

 and others. The order suggested is chalcopyrite near the wall 

 rock, then pyrrhotite bearing nickel, and lastly nickel sulphide; 

 the matrix being norite. According to D. H. Browne the occur- 

 rence of the ores at Sudbury is comparable to the phenomena 

 observed in a cooling copper-nickel matte, in which the copper 

 sulphides concentrate along the margins of the mass, and the 

 nickel sulphides at the center (Fig. 120). 



According to W. Campbell and C. W. Knight the Sudbury 

 ores were all formed from solution. The order given is as follows : 



