86 STUDIES IN GEOLOGY, No. i 



is elevated to a second bin with an automatic feed to a 

 Hardinge conical mill. The total quantity of oil used for 

 flotation is i kg. per ton of ore, and 2 /$ of this is added in 

 the Hardinge mill. The mill pulp is run into a Dorr 

 classifier, the oversize of which goes to a second Hardinge 

 mill and the pulp returned to the classifier. The under- 

 size of the classifier is dewatered in three Callow tanks. 

 The waters are returned to the mills and the settlings pass 

 to a battery of 6 mineral separation cells at which point the 

 other y$ of the oil is added. The tailings of the flotation 

 cells, carrying 2-^/2 per cent copper, are discarded. The 

 concentrates are treated in a second battery of 2 cells, the 

 tailings of which are sent back to the first battery and the 

 concentrates to a settling tank in which lime and oil are 

 added to hasten settling. These settlings are dewatered 

 in an Oliver filter and the pulp dried on a conveyor over 

 an oil-fired furnace. Two sacking machines bag the dried 

 concentrates in 50 kg. sacks. The mill treats 120 to 150 

 tons of 7 to 8 per cent copper ore and yields 350 to 400 

 sacks, or 17^ to 20 tons of 55 per cent copper concen- 

 trates. 



A lixiviation plant with a capacity of 12 tons daily was 

 under construction in 1919 to treat the lower grade oxidized 

 ores that had to be rejected in the hand-sorting of the 

 high-grade shipping ore. The plan was to leach with 

 sulphuric acid and precipitate the copper with scrap iron. 



The production of sulphide ores has temporarily dis- 

 placed that of native copper ores, because the tenor of the 

 former is two to three times that of the latter and they 

 are consequently much more profitable to handle. So fai 

 as the distribution and occurrence of the two classes of 

 ores is now known, the greater tonnage of reserves lies 

 in the native copper ores and they will again at some 

 future time be the more important type. 



