130 THE PROSPECTOR'S HANDBOOK. 



coarse a state, or when the presence of another metal or 

 metallic compound, such, for instance, as copper, might 

 interfere with the operation. In such a case, the agent 

 might attack such ingredient of the ore, rather than the 

 gold, unless means were adopted to obviate this. A thorough 

 analysis of samples of ore should be always made, and the 

 merits and demerits of a proposed process thoroughly 

 investigated by someone of experience, before any particular 

 "plant" is constructed, or any method adopted for the 

 treatment of the ore in a mine. 



Sometimes more than one process is advisable in the 

 treatment of ore ; for example, as often is the case in the 

 Transvaal, the crushed quartz may be first subjected to the 

 amalgamation process, the sulphide concentrates to the 

 chlorination, and the tailings to the cyanide. Especially is 

 this the case where such minerals as antimony, sulphide, 

 zinc blende, and other sulphides, are present in quantity. 

 Very frequently such ores, though they may assay fairly 

 well for gold and silver, cannot be smelted profitably, 

 especially in out-of-the-way districts, where everything 

 freightage, fluxes, labour, &c. is expensive. 



In the foregoing remarks no notice of that which fre- 

 quently constitutes one of the chief elements of success in 

 the prosperity of a mine, viz. : concentration, has been taken. 



The concentration may be applied, for instance, in the 

 collection of the heavier portions of the ore, crushed finely 

 or coarsely, and is applicable not only to the ore before any 

 other operations take place, but also to the " tailings." It 

 is effected sometimes by one machine, sometimes by several, 

 classification of the ore being made with regard to size or 

 weight of the small particles of pieces of ore. 



Just as the heavy grains sink to the bottom of the gold- 

 washer's " pan," so, on a larger scale, do they in the " toss- 

 ing tub," the " dolly," or "kieve." 



So if mixed, finely divided ore or sand, containing, for 

 example, all sorts of minerals, such as gold, iron compounds, 

 &c., copper pyrites and earthy matter or quartz, be shaken 

 together with water, the lighter matter settles down above 

 the " heavier." 



