158 On Gold Refining by Chlorine Gas. 



silver. This approaches in composition the gold from the pro- 

 ductive Thames district of New Zealand ; while the gold from 

 Nerrigundah in the south only contains 1*5 per cent, of silver, 

 the remaining 98-^- per cent, being gold with a trace of copper. 



An interesting and as yet unanswered question here arises, — 

 is this argentiferous character in any way connected with the 

 geological structure of the district ? 



It is a fact, and certainly a very curious one, whether it arises 

 from accidental causes, or whether it may hereafter be traced to 

 peculiarity in the rocks whence the gold of the different districts 

 is derived, that its quality or fineness deteriorates the farther 

 north we go. In other words, it contains more silver and less 

 gold. 



Thus the average fineness of Victorian gold is about 23 carats, 

 that is to say, it contains about 96 per cent, of gold and 3^ of 

 silver, with % per cent, of base metals ; while, on passing north, 

 we find the average fineness of New South "Wales gold to be 

 only 22 carats 1-f- grain, or to contain 93^ per cent, of 

 gold and 6 per cent, of silver. On going still farther north to 

 the colony of Queensland, the average fineness is little more than 

 21 carats (considerably below standard) or it contains 87i per 

 cent, of gold and 12 per cent, of silver ; that from Maryborough 

 containing as much as 14 per cent, of silver and only 85 per 

 cent, of gold. 



These are averages only. It is not to be supposed that there 

 is a regular and consecutive diminution in fineness with every 

 degree of latitude we go north. There are exceptional localities 

 in the north of this colony where the gold found is of a high 

 degree of purity, as at Rocky River, where it is over 23 carats 

 fine, or 96 per cent. 



Possibly at a future time our geologists may be able to throw 

 some light on these curious facts, and the exceptional cases may 

 then even help in explaining the apparently general rule. 



The point, however, of principal interest, as far as regards the 

 subject of this paper consists in the fact that, as the alloy 

 obtained by the gold miner is poorer in gold, it is proportionally 

 richer in silver. 



According to the published returns, 6,820,198 ounces of gold 

 have been received for coinage in the Sydney Mint, between its 

 establishment in May, 1855, and December 31, 1868. 



The average assay of this quantity would be about 943. In 

 other words it contained 94^ per cent, of gold, 5 per cent of 

 silver, and f per cent of base metals. 



Allowing an average loss of 2 per cent, in melting the gold 

 dust, there would remain, after smelting, 6,683,795 ounces of 

 bullion, and as the silver it contained amounted to 5 per cent, 

 of this quantity, the gross amount of silver in the gold received 



