T. L. Walker — Nickeliferous Pyrite from Ontario. 313 



Nickel 4-34$ 



Iron - 39-70 



Sulphur 49-31 



Moisture.. _ -10 



Copper traces 



Insoluble 5*76 



Arsenic none 



Seeing that the mineral so closely resembles pyrite, and 

 knowing that iron and nickel are isomorphous in many of 

 their compounds, it is reasonable to regard this mineral as 

 pyrite in which part of the iron is replaced by nickel ; its com- 

 position will then be represented by the formula [FeNi]S 2 . 

 When thus considered the above analysis may be represented 

 as follows : 



Nlckel 4 ' 34 ^NiS 9-12* 



( 4--1R l x>1 °2 v lift 



Sulphur 49-31^ ] l'° 



Iron 39-70 -I v . 



' y Fe O 1*02 



Oxygen (calculated) -28 ) * * 



Water -10 



Insoluble 5'76 



Total . 99-49$ 



Doubtless some of the rock-forming minerals, such as chlor- 

 ite, dissolved in the acids used for solution, but the silica of 

 such would be contained in the insoluble proportion. The 

 small portion of bases belonging to these minerals was not 

 estimated. 



A common view with regard to the structure of many of the 

 Sudbury iron-nickel sulphides, is that they are best explained 

 as pyrite or pyrrhotite containing millerite in a finely dissemin- 

 ated form. This would be hard to hold in the present case, 

 for even if we were to consider the whole of the iron as occur- 

 ring in the form of pyrite (FeS 2 ), (though we are certain that 

 some of the iron is present as magnetite), the 39*70 per cent 

 of iron would require 45'36 percent of sulphur, leaving 3*95 

 per cent sulphur to combine with the 4'34 per cent of nickel. 

 This quantity of nickel in the state of millerite would require 

 only 2 - 39 per cent sulphur, while in the state of the theo- 

 retical di-sulphide (NiS 2 ) it would require 4*78 per cent sul- 

 phur, which is a quantity not very different from that remain- 

 ing to unite with the nickel, even after all the iron has been 

 calculated as pyrite. By allowing "78 per cent of the iron to 

 be present in the form of magnetite, the agreement between 

 the theory and the analyses is complete. 



