THE CYANIDE PROCESS AS A GOLD-SAVER.

Otago Witness, Issue 2097, 3 May 1894, Page 16

THE CYANIDE PROCESS AS A GOLD-SAVER.

(By Our Wakatipu Coruespondknt.)

The account of the cyanide plant at the Premier mine, Macetown, which appeared recently in these columns, opens a new prospect for miners and mining enterprise in all localities where fine gold difficult to save has to be dealt with. It goes without saying that the cyanide process is as applicable to alluvial as to quartz gold, and it is with the former the. present article chiefly concerns itself. Anyone who has watched the progress of what may be called THE HISTOBY OF GOLD SAVING APPLIANCES must have noticed that those inventions which grade or sift the alluvial drift containing fine, and very fine, gold have caught on the mining mind with a peculiar tenacity, so that it is now safe to say that the bulk of the fine gold saved in Otago is secured by some kind or other of sorting process. Here we have at once the key to the solution of the difficult and much discussed question, " How to tave the fine gold." With proper appliances for grading alluvial auriferous drifts or washdirt;, reducing it to the smallest minimum in bulk, and treating the residue by the cyanide process, there should be no difficulty in the near future of increasing the yield from all alluvial mines and opening new fields for mining enterprise that are now pronounced duffer ground.

There is scarcely a gold field in Otago where fine gold is not found mixed up promiscuously with the alluvium that covers the bedrocks of the southern portion of our island. The quantities of the gold bo mixed up may vary, but its presence remains an incontrovertible fact.

THE MOST SURPRISING PHASK

in the whole question is that there are no reliable data or even estimates of the amount of fine gold contained in the washdirt before treatment by the sluicing or any other process, nor of the amount of gold lost in the progress of the treatment. Considering that gold mining has now been carried on for upwards of 30 years in these latitudes, it does not uay much for the acateness of our hydraulic sluicers and engineers that they have not ascertained by accurate chemical assay the value of the gold-bear-ing drifts in their claims, and also by the same means tke amount of gold carried away and lost by the process of the treatment applied. No doubt at first sight many "practical" miners will laugh to scorn the bare idea of submitting washdirt to chemical assay with a view to ascertaining its value, and dismiss from their minds all such notions as chimerical, writing down the propounder as a visionary idiot. But then strong feelings and strong langaage do not nowadays pass for argument. It will perhaps be new 3to such scoffers to hear that something of the kind is done in many large quartz mines, such as the Premier Consolidated at Macetown, for instance. As this mine is near home, the modus operandi adopted there may serve the purpose of illustration. A COMPLETE LABORATORY • for the purpose of assaying is fitted up in a building by itself, and is in the charge of a competent chemist (Mr F. Fitzgerald, of the Dunedin School of Mines), whose duty it is to make daily assays of stone from every one of the faces at work, and also from the quartz after it has been mixed in the bins of the battery just before it is put through the mill. Then, again, daily assays are made of the tailings as they pass from the berdan, which enables the management to tell whether the mill is working right or the blanket strakea are saving the gold. Accurate records of all these assay returns are kept, reference to which will at once show whether or not the mill and blanket strakes are doing their duty. And now as to the usefulness of these tests. Not only do they indicate the variations in the loss of gold, but these assays, and their records also, show the falling off or the increase in the value of the stone as it is broken out from the face of the workings — a valuable assistance to the mine manager. There is still something to be added on the score of reliability of the tests for furnishing reliable data. These tests have been found sufficiently reliable to arrive by them at the amount of bullion to be expected at any cleaning up, showing that the assays are correct as to the information they convey. When such most desirable results can be attained in quartz mining, why cannot the same system be adopted in prospecting and working alluvial mines ? And there can be no manner of doubt but that the information disclosed by these assays has as equally important a bearing upon alluvial as upon quartz mining. This statement requires no further exposition. In former articles in this column the writer has repeatedly ventured to predict that at no distant date tailings from sluicing claims would be chemically treated for the fine gold they now carry away, and which is thus lost •to the miner ; and it would appear that the cyanide process, as conducted by the Cassell Cyanide Company, is already paving the way to the fulfilment of the prediction.

In a future article the whole question will be further considered in its technical as well as in its practical aspects.