38 



carried to or near the surface in magmas and are extended 

 from them in the manner of pegmatite dikes, after the re- 

 mainder of the magma has been partially cooled and 

 crystallised. They are deposited from essentially aqueous 

 solutions mixed in varying . proportions with solutions of 

 quartz and the silicates." He has evidently in mind the 

 usual theory of the formation of the Kiruna and other 

 magnetite deposits in northern Sweden. In his special 

 reference to the Moose Mountain deposit he mentions that 

 the ore shows " such intimate relations with greenstones as 

 to suggest a direct derivation from them." 



It should be stated, however, that some of this richer ore 

 is interbanded with belts of the poorer silicious type making 

 up the majority of the whole series of deposits, and it is 

 possible that the downward percolation of hot waters may 

 have produced the enrichment. The latest effect of cir- 

 culating fluids, the formation of epidote, is generally accom- 

 panied by an enrichment of the ore near the small veins of 

 •that mineral. 



Moose Mountain has been the first iron mine in Canada 

 to concentrate its ores magnetically on a commercial scale. 

 The higher grade ore is crushed to about inch size and 

 separated from the intermixed epidote and hornblende by 

 magnetic means, raising its iron contents to a merchantable 

 grade containing 55.50 per cent, of metallic iron. The 

 plant in use, though small and experimental, has provided 

 155,000 tons of ore for shipment. 



This method is not effective for the 36 per cent, ore in 

 which the magnetite is intimately mixed with silica, and 

 within the past two years a new concentrating mill, much 

 larger and more elaborate, has been erected. Here the ore 

 is crushed to 100 mesh and separated magnetically by the 

 Grondal method. The finely divided magnetite is then com- 

 pressed to drive off most of the water, briquetted and finally 

 treated in a furnace which sinters it slightly and transforms 

 most of the magnetite into hematite. 



Though not so large as the great magnetite deposits at 

 Kiruna and elsewhere in northern Sweden, Moose 

 Mountain promises to become a great producer of ore. The 

 Keewatin iron deposits of Ontario, with the exception of 

 the Helen and Magpie Iron Mines near lake Superior, are 

 usually similar to the one just described at Moose Mountain. 



