126 THE PROSPECTOR'S HANDBOOK. 



the best one for treating any particular kind of metalliferous 

 ore. Besides, that which suits an ore in one locality may 

 be quite unsuitable, for reasons already explained, for that 

 in another. 



Perhaps the best way to approach this subject of metal- 

 lurgy is to consider one of the methods which may be 

 rightly termed complex, viz., extraction of copper from cop- 

 per pyrites. 



Copper from Copper Pyrites and other Sulphides. 



Calcination (to get rid of sulphur, arsenic, &c.) ; fusion 

 with " metal slag " (containing a proportion of silica, iron 

 oxide, &c.) and other copper ores, in order to obtain a regu- 

 lus or matte (which contains sulphides of copper and iron) ; 

 calcination of the crushed regulus ; fusion of this to get 

 rid of iron (in this process copper oxide or carbonate is 

 added, also certain slags which contain silica, &c.) ; roasting 

 of the regulus to obtain blistered copper. 



This process depends on the fact that copper possesses 

 for sulphur a greater affinity than iron does. Thus when a 

 mixture of the oxides and sulphides of iron and copper are 

 fused together the iron combines with the oxygen and the 

 copper with the sulphur, a mixed sulphide of the two metals 

 resulting if there is not sufficient oxygen present to com- 

 bine with the whole of the iron. The iron oxide so pro- 

 duced can be slagged away by the aid of silica, and the cop- 

 per collected, more or less free from iron, in the form of a 

 fused sulphide regulus. 



There are two main methods of copper smelting the 

 reverberatory and the blast furnace methods. In the for- 

 mer the copper sulphide produced in the above manner is 

 partially roasted to oxide, and the oxide so formed allowed 

 to react on the residual sulphide, metallic copper being the 

 result. 



In the other, the nearly pure sulphide "white" or 

 " pimple metal " is roasted almost completely to oxide, 

 which is then reduced by the aid of carbon in some form. 



The wet methods are mainly two. In the one the copper 

 sulphide is roasted to sulphate, which can then be extracted 

 with water, the copper being afterwards precipitated by 



