2 64 
PROCEEDINGS OE SECTION B. 
SMELTING. 
At Aldershot the auriferous pyrites, complex ores, &c., are being 
made up in suitable mixtures for calcining ; and the slagged material 
is afterwards smelted with roasted mattes, oxidised lead ores, and 
limestone in a large blast furnace to a rich auriferous silver lead, which 
is partly refined at the works, partly sent to England. 
The extraction is a very high one, as the works guarantee to pay 
from 90 to 97 per cent, of the assay value at £4 per ounce, less £2 to 
£3 per ton treatment charge. Special rebates are being allowed for 
an excess of iron in pyrites, which thus assist in reducing the cost of 
treatment per ton. 
CYANIDING. 
Although there can be no doubt that this process will have a 
future before it in Queensland, its adaptability, especially in such 
places where it has to compete with chlorination and smelting works, 
for high-grade concentrates and slimes must necessarily be confined 
to the treatment of tail in gs* 
Its work on the “Band” deserves certainly to be called a 
metallurgical achievement, but it must not be overlooked that almost 
up to date the “Hand” tailings consisted of a free milling material 
which was thoroughly suited to the extraction by cyanogen. 
In Queensland, where we have to deal mainly with pyritiferous 
ores very often of a complex character, the conditions are somewhat 
altered. Nevertheless, there will always remain sufficient scope for 
the many admirable points of this process to extend its usefulness in 
Queensland. 
The general requirements for a successful and economical 
operation of the process may shortly be stated as follows : — 
Eirst. — A fine division of the gold in the material. 
Second. — Low-grade material, free of galenite, zincblende, and 
copper minerals, though it has been claimed that the 
presence of small quantities of the latter does not seriously 
interfere with the cyaniding. 
Third. — The neutralising of acid material containing ferrous 
and ferric sulphates and basic sulphates, with lime or 
alkalies before cyaniding. 
Eourth. — The material must possess good leaching properties, 
in order to facilitate percolation ; but experience and an 
intelligent handling of the slimy material may, in some 
cases, overcome the obstacles generally encountered in the 
percolation of slimes. 
The average extraction from 5 to 10 dwt. stuff may be taken as 
70 per cent, to SO per cent. ; while, under favourable conditions, 
concentrates assaying from 3 to 4 oz. per ton may give an extraction 
of 90 per cent, to 95 per cent, in three or four weeks’ treatment. 
According to W. B. Eeldtmann, in the American Engineering and 
Mining Journal, only very weak solutions are being used in the 
presence of any metals having an affinity for cyanogen. 
The strength of the first solution may vary from 025 to 0*50, 
while the number and strength of subsequent solutions and washes, 
and the time of contact required, depend entirely on the quantity and 
nature of the ore. 
