262 
PROCEEDINGS OF SECTION B. 
The above tests were made in duplicates, and from the results 
obtained in Test V. it mav be safely concluded that a still higher 
addition of salt would have brought about a somewhat higher percentage 
of extraction. However, as the regrinding of the material to such a 
fine mesh, together with the additional cost of, say, at least 15 per cent, 
of salt, formed two very important economic considerations, the 
company finally decided to sell the concentrates to smelting works, 
which were able to guarantee better returns than could possibly have 
been obtained at the mine. 
The greater part of the gold undoubtedly existed in these 
concent rates, as telluride of gold, in conjunction with bismuth telluride, 
and sulphide. 
Under the present system of gold-milling, the writer estimates 
that over 20,000 tons of silicious concentrates and slimes should be 
available for further treatment every year, exclusive of old tailing 
heaps. 
D.-COMPARATIVELY RICH ORES WITHOUT OR WITH VERY LITTLE 
SULPHURETS. 
This class is mainly represented by the Mount Morgan ore, the 
character of which is so sufficiently known now as not to require a 
further description. 
E.— ARGENTIFEROUS GOLD ORES AND EXCEPTIONAL ORES. 
Some of the Croydon gold ores are distinctly argentiferous in 
character. A parcel of 10 tons, which was submitted to the writer, 
assayed 51 oz. silver to 2*4 oz. gold per ton; it was a “ dry” ore with 
95 per cent, of SiO a . 
A number of shallow workings at Boolboonda used to produce a 
semi-oxidised argent if cro us and auriferous copper pyrite, of which the 
following assays are representative examples : — 
No. 1.— Cu. 15*4 No. 2.— 13*8 
Au. 0*85 oz. 12 oz. 
Ag. 37 „ 20 „ 
Quite recently a parcel of about one ton, consisting of an 
apparently crushed and washed quartz from Mount Morinish (Rock- 
hampton), was submitted for treatment. Upon being assayed it gave 
10*5 oz. of gold, also 2'8 per cent, of copper. 
A further investigation showed the copper to be present as very 
fine and laminated particles of native copper, which was found to be 
alloyed with the greater portion of the gold. 
The stone used to be reduced at a local crushing-miR, but, to the 
great disgust of the owners of the mine, after cleaning up and 
retorting, the results, though very bulky, only consisted of auriferous 
metallic copper. A number of" these retort residues have passed 
through the hands of the writer, and, although varying in richness, 
very rarely carried more than 2 '5 per cent, of gold. 
Efforts are being made at present to find a rational method for 
the treatment of this stone. 
