REFRACTORY GOLD ORES OF QUEENSLAND. 
268 
THE TREATMENT OF REFRACTORY GOLD ORES IN QUEENSLAND. 
It has often been said that Queensland offers a large field to the 
inventor of new processes for the extraction of gold. 
As already pointed out in the previous paragraphs, the Queensland 
milling methods may he improved upon ; but the writer would rather 
prefer to see these improvements brought about on lines of well- 
established metallurgical practices. At present Queensland is well 
provided with metallurgical works, which are fully able to deal with 
the refractory gold ores of the colony, so as to leave very little room 
for improvement in that respect. 
We find large chlorination works at Mount Morgan, also on a 
smaller scale at Charters Towers and Pavei iswood ; there are general 
smelting works at Aldershot, which arc dealing with a large quantity 
of auriferous material ; and, fiually, we have the cyanide process with 
well-established works at Charters Towers, Croydon, and Georgetown. 
Each of these three, metallurgical methods has its special sphere 
of usefulness, and no doubt in time their beneficial influence will be 
felt in every Queensland mining centre. 
CHLORINATION. 
A few years ago “ barrel ” chlorination was the usual application 
of this process in Queensland, with the exception of the Charters 
Towers pyrites works, which have always used the chlorine vats. 
Economic considerations, apparently, are responsible for the return to 
vats, which, however, are being erected of a much larger size than 
heretofore. At Mount Morgan vats holding about 25 tons of charge 
have replaced the barrels and smaller vats. The chlorine is being 
applied there now as chlorine water, for which it is claimed that the 
consumption of the solvent can be better controlled and kept within 
the absolute requirements for the extraction of the gold. 
The use of chloride of lime and sulphuric acid has been superseded 
again by manganese, salt and sulphuric acid, and the installation of 
chlorine stills, towers, and solution tanks. 
The official report of the Mount Morgan Company, Limited, for 
the year ended 81st May, 1891, places the extraction within a small 
fraction of 95 per cent, of the assay value of the ore; and as 65,076 
tons, assaying 1*66 oz. of gold per ton, have been treated during the 
year, the metallurgical results must be considered highly satisfactory. 
The percentage of extraction of the smaller works could not he 
ascertained, but it may be safely assumed that equally good results 
are being obtained by them, varying, however, with the adaptability of 
the material under treatment. 
The actual cost of chlorination at Mount Morgan, including 
milling and calcining, is about 15s. per ton ; but it is expected that, 
with the introduction of a larger number of revolving furnaces and 
other facilities for the automatic handling of the material, the cost 
wili be brought down to 12s. per ton. The cost at the smaller works 
may be put down as varying between 15s. and 25s. per ton. It must 
be mentioned here that these figures compare favourably with the cost 
of chlorination carried on under similar conditions elsewhere. 
Public chlorination works generally guarantee 90 per cent, of the 
gold contents at £4 per ounce, less £2 to £3 per ton for treatment, 
unless special arrangements have been made for a different settlement. 
