COROCORO COPPER DISTRICT OF BOLIVIA 83 



Lumps too large for the crusher were broken with sledges 

 and the ore fed to the crusher by hand. The crushed ore 

 was ground in four Chilean mills. The pulp from each 

 mill was passed over a screen with %" x y 2 " openings and 

 the oversize shoveled back into the mill from which it came. 

 The pulp was elevated to a 1/16" impact screen and the 

 oversize sent back to the mills. The undersize was classified 

 in a 6-spigot hydraulic classifier, making 3 sizes, 2 spigots 

 to a size, each of which fed one of three jigs. The jigs 

 were 3-compartment Harz jigs with 1/16" screens. The 

 three hutch products of the three jigs were mixed to form 

 a first concentrate averaging 50 to 60 per cent copper. This 

 was retreated on a fourth jig to make a final product with 

 a tenor of 85 to 90 per cent copper in the first compartment, 

 the products of the second and third compartments being 

 retreated on the same jig. The tailings of the four jigs 

 were reground in the Chilean mills. The overflow of the 

 classifier was settled in a spitzkasten and distributed to 3 

 Overstrom tables which made a concentrate that was 

 retreated on a fourth table and tailings averaging .3 to .5 

 per cent copper which were discarded. The tailings of the 

 fourth table were also discarded, the middlings were 

 retreated on it ; and the concentrates were a final ''barilla" 

 running as high as 95 per cent copper. The capacity of 

 the mill was 300 tons per day and its recovery was given 

 at 85 to 90 per cent. The barilla was sun-dried on an open 

 stone floor and packed for shipment Ninety per cent of 

 the barilla was produced by the jigs and 10 per cent by the 

 tables. 



From 1912 to 1918 the Compania Corocoro de Bolivia 

 supplemented its output of native copper ores by shipping 

 considerable quantities of hand-sorted copper sulphide and 

 sulphate ores which carried 18 per cent or more copper. 

 In 1918 the San Francisco mill was converted into a 

 flotation plant, the mining of native copper ores suspended, 

 and the mill utilized for the treatment of low grade sulphide 

 ores. The ore is now crushed in a n x 18" jaw crusher 



