

USEFUL METALS 241 



brought up from below. At all events they are not primary 



segregations. 



Morenosite, the sulphate of nickel, and zaratite, the carbonate 

 of nickel, are formed by the oxidation and carbonation of the 

 sulphides and other ores of the metal. 



The hydrous silicates of nickel, which are rarely, if ever, 

 definite mineral species, but rather a mixture of the silicates of 

 nickel with magnesium compounds and free silica, are entirely 

 unlike the sulphides and arsenides in their genesis. They form 

 a distinct class of ores. They are associated with masses of 

 serpentine or other hydromagnesian rocks. They represent a 

 concentration of the nickel in a peridotite magma, but especially 

 one rich in nickeliferous olivine. 



Character of the Ore Bodies. Millerite occurs as an incrusta- 

 tion upon other minerals and as capillary crystals in cavities 

 among quartz crystals. The nickeliferous pyrrhotite occurs as 

 a contact deposit between quartzite and norite; also in irregular 

 masses of large dimensions. The sulphides and arsenides appear 

 in well-defined fissure veins traversing the basic intrusives and 

 their adjacent terranes. Garnierite and genthite, together with 

 other hydrous silicates of nickel occur in enormous deposits 

 which in part result from precipitation and in part from the 

 transition of a peridotite magma to serpentine. 



The deposit near Noumea, the capital of New Caledonia, is 

 perhaps the most noted nickel-bearing ore body in the world. 

 The ores are particularly free from sulphur, arsenic and copper, 

 three constituents injurious to nickel. There are two distinct 

 varieties of these hydrous silicates present. The one is green 

 and the other is chocolate brown. The green variety carries 

 from 45 to 48 per cent, of nickel oxide; the brown variety carries 

 from 43 to 46 per cent, of the oxide of nickel. Both contain 

 small quantities of cobalt. The green variety was long mistaken 

 for the green hydrous carbonate of copper, malachite. The 

 brown variety was thrown away as worthless earth which was 

 supposed to be colored by the hydrated oxides of iron. The 

 green variety is now regarded as deposited from solution from 

 above, while the brown variety tells its tale of the transition of 

 the country rock peridotite to serpentine. 



The method of mining at Noumea is simply open cut work. 

 The ore is taken out in benches having faces about 30 ft. high 

 so that the appearance of the quarry is not unlike the risers and 



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