REFRACTORY GOLD ORES OF QUEENSLAND. 
261 
Unfortunately, as in many cases of this kind, no attempt liad been 
made to ascertain if the material would be suitable for chloriuation, 
although it must be said, in justice to the management, that a casual 
observer, even it an expert, would not have noticed by the mere 
appearance of the rather sandy material that it contained anything 
detrimental to the extraction of gold by chlorine. The plant was in 
charge of an experienced metallurgist, who simply carried out the 
instruction of the management to chlorinate the “stuff.” The results 
were somewhat disastrous, as it was found that more than 80 per cent, 
of the gold remained in the tailings. At that juncture the pro- 
fessional advice of the writer was requested, and the concentrates 
submitted to a complete quantitative analysis, with the following 
results : — 
SiO„ 
44-90 
A1 2 0 3 
8*82 
Ee 
18-98 
partly combined with S ; 
partly oxidised. 
S 
11-71 
As 
2-07 
CaO 
2-80 
Gold assay per ton, 4*35 oz. 
MgO 
ro5 
Te 
0/56 
Bi 
1-26 
H 2 () -|- Au 
7-85 
found by difference. 
100-00 
As the management was naturally anxious to adapt the ore to 
the existing plant, which had cost over £3,000, an average sample, as 
represented by the above analysis, was subjected to a number of 
laboratory tests with the main object of finding some means for a 
better extraction by chlorination. 
Test I. — A sample of 4 oz., after roasting in the muffle at a 
dull red heat and chlorinating, only helped to confirm the 
failure of the extraction as experienced on the larger scale. 
Test II. — The material was ground to pass an SO- mesh sieve, 
and roasted with the addition of 5 per cent, of salt. The 
chlorination yielded 53^j per cent, of the total gold 
contents. 
Test III. — The same material roasted with the addition of 
10 per cent, salt gave by chlorination an extraction of 
78 t \j per cent. 
Test IV. — The original concentrates without further grinding 
were roasted with the addition of 15 per cent. salt. Loss 
of gold in roasting was 6-^- per cent. Total extraction of 
gold by chlorination, 72 per cent. 
Test Y. — The finely -ground material (80-mesh) roasted with 
15 per cent, salt, which was gradually added, showed a loss 
of gold in roasting of 3 per cent., while chlorination 
extracted 87 per cent, of the original gold contents. 
Test YI. — Dilute cyanide solutions of various strengths gave 
indifferent results. 
