BY HON. A. C. GREGORY, C.M.G., F.R.(i.S., ETC. 



143 



quartz, i-emaiii ; and the only difficulty is the finely divided 

 condition of the precious metal ; but as the workings pro- 

 gress, the pyrites will present itself in a less decomposed state, 

 and eventually when the level of permanent water is reached, 

 the whole will appear in the condition of a bright, brassy- 

 colored " mundic," in which the gold will be contained in such 

 minute particles as to resist direct amalgamation, and the ore 

 will have to be roasted at a low heat to di'ive off the sulphur. 



Hitherto this roasting process has been the stumbling block 

 of the miner in this colony. They know that a low heat will 

 slowly set free the gold in the sulphide, and therefore assume 

 that more heat will do the work quicker ; but the higher heat 

 partially fuses the ore, and the gold is hopelessly entangled and 

 lost, and it is for this reason that kiln or clamp bui-ning quartz, 

 though rendering it easier to crush, has failed in economic 

 results. 



The process best suited for working auriferous pyrites is first 

 to crush the stone and then to concentrate the pyrites by wash- 

 ing. It is then roasted at a low heat ; at first so low that it is 

 scarcely red hot, the greatest care being taken to avoid fusion. 

 When the sulphur is driven off in the coTidition of sulphurous 

 acid, and the iron being oxidized to a fine red powder, from 

 which the goid may be sepai'ated by amalgamation in any of the 

 pans, or other amalgamators, one important feature being that 

 the rubbing surfaces should be in part wrought iron, the 

 chemical reaction of which assists in keeping the mercuiy in 

 proper condition to take up the gold. 



