COPPER ORES. 1163 



Still higher up, chalcocite may appear with the chalcopyrite and bom- 

 ite. For a short distance below the level of ground water this mineral in 

 some mines is the dominant sulphide and may be produced by the reaction 

 of cupric sulphate on the iron sulphide. For ferrous sulphide the reaction 

 in the presence of oxygen would be : 



( 1 ) 2FeS+2CuS0 4 +20=Cu 2 S+2FeS0 4 +S0 2 



For iron bisulphide in the presence of oxygen, the reaction would be: 



(2) 2FeS,+2CuS0 4 +60=Cu 2 S+2FeS0 4 +3S0 2 



or, if oxygen be absent, the reaction is: 



(3) 5FeS 2 +14CuS0 4 -fl2H 2 0=7CujS+5FeS0 4 +12H 2 S0 4 



Chalcocite may be produced also by the reaction of cuprous salts on 

 iron sulphide. For ferrous sulphide in the presence of oxygen the reaction is : 



(4) FeS+Cu 2 S0 4 =Cu 2 S+FeS0 4 



for iron bisulphide in presence of oxvgen: 



(5) FeS 2 +Cu 2 S0 4 +20=Cu,S+FeS0 4 +S0 2 



or, if oxygen be absent, 



(6) 4FeS 2 4-7Cu 2 S0 4 +4H 2 0=7Cu„S+4FeS0 4 +4H 2 S0 4 



Furthermore, the chalcocite may be produced by reactions of the sul- 

 phates either on the chalcopyrite or on the bornite. In the case of cupric 

 sulphate upon chalcopyrite in the presence of oxygen, the reaction may be 

 written as follows: 



(7) CuFeS 2 ^CuS0 4 +20=Cu,S-LFeS0 4 +S0 2 



or, if oxygen be not present, the reaction may be as follows: 



(8) 5CuFeS 2 +HCuS0 4 +8H 2 0=8Cu 2 S+5FeS0 4 +8H 2 S0 4 



For cuprous sulphate upon chalcopyrite, in the presence of oxygen, 

 the reaction is: 



(9 1 2CuFeS,+Cu 2 S0 4 +60=2Cu 2 S+2FeS0 4 +S0 2 



and in the absence of oxygen is : 



( 10) SCuFeS 2 -i-llCu 2 S0 4 ^4H,.0=150u,S+8FeS0 4 -f4H 2 S0 4 



