84 STUDIES IN GEOLOGY, No. i 



and ground in two Allis Chalmers ball mills. The mill 

 pulp is elevated to a Dorr classifier, the oversize of which 

 goes back to the mills. The undersize goes to a battery of 

 20 flotation cells which are of a modified Callow type. 

 The concentrates are run into i5Oton settling tanks and 

 the tailings through another series of 10 cells, the con- 

 centrates of which go to the settling tanks. The tailings 

 of the second battery of cells are distributed to three But- 

 chart tables which yield a native copper concentrate and 

 tailings carrying i- l / 2 per cent copper which are discarded. 

 The settlings of the tanks are filtered on Oliver and Port- 

 land filters. In the flotation cells i kg. of oil is used per ton 

 of ore. In 1919 the daily output was 200 to 250 tons of 

 7 to 8 per cent ore, 180 to 200 tons of which came from 

 the Remedies mine, which yielded 20 to 25 tons of 45 per 

 cent flotation concentrates and i- l /2 tons of native copper 

 concentrates. 



Formerly both the large Corocoro companies generated 

 steam power with taquia, or llama dung, fuel. This sold 

 at about $7.00 per ton and nearly $125,000 of it was 

 purchased annually by them. Diesel engines have been 

 substituted for steam power and with the falling off in 

 demand for taquia, the local price has dropped to less than 

 half the above price. The Compania Corocoro de Bolivia 

 has two batteries of 4 Diesel engines, each battery capable 

 of furnishing 125 H. P. to generate power for the mines 

 and two batteries of 6 Diesel engines, each capable of 275 

 H. P. for the mill. One battery in each case is held in 

 reserve for emergency use. The Corocoro United Copper 

 Mines, Ltd. has also replaced nearly all its steam engines 

 with Diesel and Peters engines. Fuel costs in the district 

 are said to be very high and to amount to 2- l / 2 to 3 cents 

 per pound of copper produced. 



The Corocoro United Copper Mines, Ltd., operates the 

 three mills for the treatment of native copper ores because 

 the water available is not sufficient for one larger mill and 

 the same water is used successively by the three mills. 



