lEON PYEITES. 



By J. Latta, Esq. 



lEead before the Royal Society, lith October, 1874.] 



Me. Thompson read the following paper on the treatment of 

 iron pyrites by Mr. J. Latta, who was unavoidably precluded 

 from being present. 



Mr. President and Gentlemen, — At the request of some of 

 the members of the Eoyal Society, I have ventured to occupy 

 part of your time this evening in describing the method of treat- 

 ing pyrites for the extraction of its gold, as carried out by the 

 Port Phillip Company at Clunes. 



In 1861 I was engaged by that Company as their chemist and 

 assayer, with special instructions to devise, if possible, a process 

 for profitably extracting the gold from their pyrites, which was 

 then but little better than a waste product. Except processes 

 inapplicable to our circumstances, such as smelting, &c., the only 

 known means for extracting gold from such mineral was that 

 practised in South America and the United States — " of exposing 

 the auriferous sulphides to the action of air and moisture for a year 

 or so, whereby a portion of the mineral became oxidised, liberat- 

 ing the gold previously enclosed by the sulphides, the mineral 

 was then passed through the stamping battery with quartz, and 

 whatever portion of the sulphides remained undecomposed was 

 retained, as well as the then rude machinery for that purpose 

 admitted, to undergo another term of oxidation, and so on 

 whilst any remained." I scarcely need to point out how extrava- 

 gantly wasteful of time and gold such a process must have been. 

 Yet even at the present time this process is occasionally practised 

 in Victoria. At some claims the blanketings — that is the pyritous 

 sand, with a little free gold caught upon the blankets — are, after 

 a time, again put through the batteries with the quartz, for the 

 purpose of extracting its gold. Any one practically acquainted 

 with the treatment of mineral containing fine gold by the battery 

 process, will at once recognise the impossibility of retaining a 

 fair proportion of such minutely divided gold as oxidised pyrites 

 aff'ords ; by far the larger portion would be held in suspension by 

 the water, and be carried away by it through all the appliances 

 devised for its retention. In addition to the difiiculty of retention 

 arising from the fine state of division which gold so obtained 

 possesses, most of these particles would be coated with iron 

 oxide, and other products of the decomposed mineral, thus 



