SEPARATION OF GOLD FROM PYRITES.

Westport Times, Volume II, Issue 205, 27 March 1868, Page 3

SEPARATION OF GOLD FROM PYRITES.

(From the Melbourne Argus.) One of the greatest problems which the quartz-miner has to deal with is, how to treat the pyrites which occur in great abundance in many of the reefs of the Colony. Where the stone is a mixture of quartz and gold only, the extrication of the latter is a matter of the greatest simplicity. But when the reef is of a pyritiferous character the wits of the miner are puzzled, and his ingenuity is exhausted in vain efforts to drive away the arsenic and sulphur. The chemist tells him by •analysis that there is plenty of gold in the quartz he is raising, but he is unable to realise more than a tithe of the precious metal; and so he goes on growling and anxious, but scarcely progressive, knowing well that his blanket-tables, his revolving pans, and his amalgamating barrels are only doing him partial service, and that fully one-half of all the gold that should be his, is passing away under his very eye 3 into the waste of the failings pit, rescued from the custody of Constable Quicksilver by Master Pyrites. This tale, however, is an old one. It has been repeated over and over again in these columns, and by at least one energetic man of science—we allude to Mr H. A. Thompson —it has been discussed before both learned bodies and meetings of plain and practical men. The best known means of dealing with the problem we have suggested, experiments have been "made successfully in their presence; •and yet in all but a few solitary instan-

ces, the waste continues, and gold to the value of at least threo-quaters of a million of money is annually thrown ■ away, it is estimated, inconsequence of the inability of the miners to deal practically with the question of how to separate gold from pyrites. This, perhaps, is not to be wondered at, however much it may he regretted. Few miners working their own claims would have been able to provide the apparatus ; necessary if they had known what that apparatus was. Very ;few even of the companies formed te work quartz mines are in a position, financially, to experiment. The condition of most of those which are known to Melbourne investors is one of chronic impecuniosity. They have not had the means to try the plans propounded for the proper treatment of pyritiferous stone. It has been poverty less than want of will, which has hitherto retarded scientific effort in dealing with the difficulty. At two mines the subject has been dealt, and, we are glad to say, with so much success that the problem may now be regarded as solved. The mines are the Port Phillip Company's at Clunes, and the Geo I Hope Company's at Crooked Eiver. At Clunes, important service has been done from time to time, by the full scientific staff maintained there, and never more so than in this matter. It was first ascertained by assays and microscopical examination, that of the precious metal lost in the process of reducing the quartz, at least three-fourth consisted of gold in a very minute state of division, deposited in and enveloped by pyrites. Two main difficulties were encountered—the separation of the finely pulverised pyrites from the more coarsely crushed sand, and then the rescue of the gold from its iron prison. After years of experiment at Clunes and elsewhere two machines have approved themselves the best for concentrating the pyrites. One is a patent circular buddle, and the other a patent modificatinn of the percussion table. The first is in use at Clunes, and the latter at the Good Hope mine. The machines bring together the pyrites, but as the sulphur and arsenic they contain prevent the use of mercury for the extraction of the gold, it is necessary to drive these off by roasting the pyrites in an oxydisingfurnacedesigned for the purpose, and to re-grind this roasted ore in mercury. By these means the Port Phillip Company have been able to save gold which would otherwise have been lost, to the extent of between £2OOO and £3OOO per annum, and although the quantity of gold has only run from 3-2- oz. to 5 oz. to the ton of pyrites—the stone obtained at Clunes being poor—the cost did not exceed £3 per ton, and the per-centage obtained was equal to 94*4 per cent., showing a loss of only 7*6 per cent, in the operation. At the Good Hope mine the same process of roasting and grinding after concentration is followed ; but as the quartz is considerably richer there, as much as 120 oz. of gold has been obtained from a single ton of pyrites. The results should encourage mining capitalists and others to turn their attention energetically to this matter. We have set down the loss now going on at three-quarters of a million sterling per annum, but we know that excellent authorities set it down at a fourth more. It is proved, not by experiment in the laboratory, but by actual practice at two mines, both working profitably, that 75 per cent, of this loss can be prevented; that the means used are neither very costly nor very difficult to manage ; and that there is no risk whatever in the employment of capital for the reduction of auriferous pyrites. This being the case, surely nothing more than publicity for the results obtained is necessary to insure the attention of the mining public to a subject of such importance to them. No mystery is made at the Port Phillip Company's works of their operations. It would not be unreasonable in such a case to ask those who are most directly interested to visit the Good Hope mine, comparatively distant and inaccessible as it is; but that is not necessary, for Clunes is easily reached from all parts of the colony, and there the process of extracting the gold from its troublesome covering can be seen in all its stages. Various attempts, it is well known, have been made by private companies to do what has been accomplished at Clunes, but their failure Should not deter the public from now taking up the matter heartily and hopefully. For years the most scientific of our miners have, as it were, been groping in the dark. It is only of recent date that they have really hit upon the contrivances and processes which are best adapted for the purpose in view. It is now for the public, general as well as mining, to step in and utilise the experience which has been gained.