36 lEON PTEITES. 



offering another Hindrance to its chance of amalgamating witli 

 the mercury. This latter difficulty deserves careful consideration, 

 where fine gold has to be dealt witti, as from its fineness it escapes 

 the scrubbing which the larger grains receive from contact with 

 the quartz whilst crushing, whereby their surfaces are cleaned, 

 and thus rendered extremely sensitive to the influence of mercury 

 placed for their detention. In reference to the condition of gold 

 in pyrites, it has come to be pretty generally admitted that 

 "nearly, if not quite all, the gold exists in the metallic state." 

 This quite agrees with the results of some experiments carried out 

 by myself in conjunction with Mr. Daintree, late of the Victorian 

 geological staff. Our researches ended in obtaining but the barest 

 possible evidence of gold existing in a mineralized state in pyrites. 

 As a matter bearing somewhat in support of this result, and 

 whilst engaged in these investigations, I had the good fortune to 

 come across some fine specimens of cubical pyrites, which upon 

 examination with a pocket lens, seemed to indicate the presence 

 of gold ; upon transferring them to a good microscope gold was 

 distinctly seen upon the planes of cleavage, and upon dissecting 

 the crystals, every cleavage was found distinctly gilded. Now, 

 from the fact that the presence of gold could only be determined 

 by the aid of a good microscope, and that only as a fine gilding, 

 some notion may be formed of the excessively fine state of its 

 division, and how unsatisfactory would be the task of separating 

 such liberated films from water in motion. 



Gruided by these considerations, it became evident that any 

 attempt to mechanically separate gold from pyrites — unless aided 

 by the previous decomposition of its enveloping sulphides — must 

 prove ineflective from the impossibility of reducing it to its ulti- 

 mate atoms, for so long as a cluster of sulphide atoms remain 

 unbroken, they might reasonably be imagined to enclose those of 

 gold. Again, it was equally clear that, when such gold toas 

 liberated from its envelope, water concentration alone was inap- 

 plicable. To test the correctness of these conclusions, each of 

 them was made the subject of rigid experiment on an extended 

 scale, before receiving them as fundamental truths to guide us in 

 determining the best method suitable to our requirements. Two 

 parcels of pyrites, of twenty tons each — one roasted, the other 

 unroasted — were ground in one of the best arrastras known, with 

 mercury ; a constant stream of water flowing through to carry off 

 the finely-ground sand, which was then carried through mercury 

 boxes and over blankets. Each parcel received the same amount 

 of grinding and treatment in every detail. The results are as 

 follows : — 



20 tons raw sand, containing 3 oz. 6 20 tons of roasted sand, 1 oz. V dwts. 

 dwts. per ton. 10 grs. of gold per ton. 



Gold obtained 29-21 p. c. Grold obtained 51-57 p. c. 



„ in tailings 42-84 „ „ in tailings 27-21 „ 



„ carried olf in water... 27-95 „ „ carried off by water... 2 1'22 „ 



