THE METALLURGY OF GOLD.

Auckland Star, Volume XXXIX, Issue 233, 29 September 1908, Page 3

THE METALLURGY OF GOLD.

AUCKLAND INSTITUTE LECTURE. ' A large attendance of members of the ' Auckland Institute gathered in the Museum Buildings last evening on the ; occasion of an interesting scientific lee- i ture on "The Metallurgy of Gold," de- • livered by Professor Jarman of the Auckland School of Mines. • Professor Jarman, -who observed that iie would devote his address to a description of the treatment of those classes of the metal found in the Auckland district, explained at length the qualities and character of the metal. Describing the malleability of gold, he ' illustrated by means of lantern slides the extraordinary extent to which gold may be beaten out—so fine as to assume, alter solution in cyanide of potassium, a transparent state, while a grain could be made to cover 60 square inches. The various alterations in colour after solution of the leaf were also the subjects ol experiments. The speaker said that they could obtain gold so pure that it could not be really ascertained whether or not any impurity were present. At some mines at Waihi, and at some other places, the gold bullion obtained was sometimes brittle, and when refined in the usual way in the mint and afterwards alloyed with copper, it was found . that the bad qualities of the selenium I were made manifest, and the gold was ' not suitable for coinage. This difficulty hac 1 now been overcome, but the amount lof selenium in the ore was so small that lit could not be seen, having been discovered by the computation that it wa3 the only thing absent in other satisfactory ores, which would account for the difficulty. The Professor then referred to the methods of extracting from the ore by means of the battery and the amalgamated copper plate. Referring to the fact that it was proposed to treat 1 the rich tailings from some of the mines at Thames, he thought that the under- I taking should Tesult very well, as from I the old workings some very rich gold j had been obtained, whilst what was now known as the "concentrate" had not ihen been treated for the second time. The chlorination process, .3 used at Mt. Morgan (Queensland) had not proved wholly satisfactory, as the chlorine had a tendency sometimes to seek out the baser metals, when these were present, rather than the gold itself. In this diffi- i culty, it had been found that the cyan- I ide process would solve the problem, and that a solution of one per cent, of cyanide had a preference for the gold, or. in other words, a selective action. I After referring at length to the appli- | cation of the cyanide process, the speaker described the sliding process, by i which was secured a large proportion of I the residue obtained after treating with I the cyanide, the methods of dealing with sl'me, the hydraulic separator, the decantation process, the tube mill, the steel etamp, the circulating tank and other ir.ining appliances. All the subjects were I illustrated with the aid of the lantern j and diagrams. At the conclusion of the lecture, a hearty vote of thanks was accorded Professor Jarman. ■