66 HATCH : THE KOLAR GOLD-FIELD. 



The working costs are high, but it is not difficult to account for 

 this. First, the nature of the ore-deposit dictates a high cost of work- 

 ing; as, for instance, the occurrence of the pay-ore in chutes, which, 

 though of high grade, are of comparatively limited extent. This 

 leads to a heavy expenditure in development, as much sinking, driv- 

 ing and cross-cutting have to be done in waste rock in order to open 

 up pay or chute-ore. The cost of this development work is included 

 in the figures for working costs given above. Then again the heavi- 

 ness or instability of the ground in parts of the mines necessitates a 

 big expenditure on timber to secure the stopes, shafts, and levels. 

 Further, it must not be forgotten that the cost of working a high- 

 grade ore is of necessity greater than that of a low-grade ore, and the 

 reason for this is plain. In mining low-grade stuff, the main object 

 is to obtain a large tonnage at a low cost ; consequently the stopes 

 are carried as wide as possible and the whole mass of the ore-body 

 is, as a rule, exploited, the exploratory or dead work being at a mini- 

 mum. With high-grade stuff, on the other hand, the stopes are kept 

 as narrow as possible and great care is exercised only to extract the 

 payable portions of the ore-body. Much exploratory work on waste 

 rock is, therefore, necessary in order to locate the pay-ore. Similar 

 factors influence the metallurgical treatment. With low-grade stuff 

 the ore is passed quickly through the mill, a high stamp-duty being 

 maintained by the use of coarse screening and a low discharge, and 

 the cyanide process is relied upon to catch the gold that escapes 

 amalgamation. Whereas with high-grade ore the usual practice 

 is to crush fine and to catch as high a percentage of the gold as 

 possible by amalgamation. 



For these reasons it is impossible to compare the working costs 

 of high-grade mines, such as those at Kolar, with the low-grade mines 

 of other countries, as, for instance, those of the Witvvatersrand in the 

 Transvaal. At the same time, it must be admitted that a reduction in 

 working expenses at Kolar could no doubt be effected by improve- 

 ments in milling plant, and by the substitution of automatic mechani- 

 cal means for native labour in the handling of the ore delivered at 



