UPPER THAMES ORElnteresting Dialogue with a Miner. [From Our Own Crrespondent.]

Te Aroha News, Volume V, Issue 217, 27 August 1887, Page 1

UPPER THAMES ORElnteresting Dialogue with a Miner. [From Our Own Crrespondent.]

WiitN' visiting Karangahake a few clays since I had an interview with an old miner, who is workingout a block on the tribute system in a certain mine, where he has now got a large tonnage of high-grade gold and silver bearing ore to grass, and an abundance of the .same class in sight ready for bieaking - out. After making a careful examination of the ore, which is laminated and streaked with "sulphides" indicating the presence of silver in that form (but of the presence of gold there was no distinguishable evidence whatever), the following dialogue ensued, and as it bears on the ores peculiar to this distiiet generally h may be mtezesfcing to some of your readers :—: — Correspondent: To those unacquainted with the character of your ore there is nothing in its appearance, when in a raw .state, that would indicate richness in either gold or silver. Now what value do you place upon this stone at per ton of '2,2-WHb? Miner : The assay value of the whole of that heap, containing about 25 tons of ore, is ceibainly not less than £20 per ton ; but, if necessary, we could " screen" it down to about 15 tons, and then the value would reach double that amount. C. : What is the use of you placing an assay value on your ore when it is stated, and is pretty generally admitted to be a fact, that the best battery plant known is not equal to saving 50 per cent, of such bullion value ? M. : 'At one time we did not think so, but we now know that the ordinary battery s> stem of ore reduction would not redeem •25 per cent, of the bullion contained in ore of this class according to its assay value, and, consequently, we are not idiotic enough to send any of it to a plant of that description for treatment, C. : Well, seeing that your digestive organs Mill not admit of your subsisting on ore in its raw state, what are you going to do v ith it in order to convert it into cash ? M. : We intend keeping it hero awaiting the result of negotiations that are now on foot for the establishment of an export trade in oie with Frieberg, London, and California. C. : lam afraid that you will find the co*t of transport to either of the places mentioned rather a heavy item. But in the e\entof jour being successful in creating an export tiade, what quantity of ore could you r,et ready for transport by the end of August? M. : With one month's notice we could biefck out 200 tons, and our " block " is now f-uffi Jently opened up to enable us to double that quantity by putting on extra hands. C. : Don't you think that it is a pity to .-end ore to a foreign market for sale when the introduction of suitable appliances for its treatment here would not only afford employment to a good number of men, but vvould also save the cost of transport, which would be an agreeable addition to your own income ? M. : We are most certainly in favour of , treating our ore locally, but charity begins at home, and we are not sufficiently patriotic to bend our ore to a plant where fully 7/5 per cent, of its value would be washed clown .stream, where it won't benefit anybody. I believe, however, that the time is not far distant when some one of the persons who are now engaged in making cxpeiiments on this ore will hit upon the correct process for saving a fair percentage of the bullion contained therein. In fact, we have now got a plant in this district known as "Railey's," which I firmly believe would extract about 75 per cent, of the bullion value of this ore if the proprietors could be induced to add a a dry crusher and roaster to their establishment. C. : Then it is your opinion that dry crushing and chloridising roasting, with careful grinding, to be followed up by hot chemical amalgamation, would save a good percentage of the bullion contained in your refractory ores ? M. : Yes, and that opinion is based on some tests that have been made in a small way with exceptionally good results. C. : You have now got a smelting furnace in this district, and as this was running here for a short time, you have doubtless been able to form an opinion as to the value of that process when applied to local ore, M. : Smelting is undoubtedly the best known system for reducing rebellious ores, because the furnace is simply a big crucible ; hence the possibility of working close up to the assay value. In fact, I have now got letters in my possession from a mining engineer in South America, where smelting operations are being carried on upon a large scale, and the writer says that they no only work up to, but they very often extract 110 per cent, on the assay value. He accounts for this by stating that the loss in cupellation when assaying is much greater in proportion than is the case when cupelling or refining the furnace bullion. But thcTcopt of treatment by the smelting process will always prohibit us from again attempting that system in this locality. The bulk of our ore is composed of silica, which requires a very large proportion of fluxes to render it amenable to the smelter ; but that work might be carried out successfully in a large seaport town such as Auckland, where coke, galena, and iron ores could be obtained at a comparatively cheap rate. C. : What is your opinion about the chlorinating process in relation to the treatment of local ore ? M. : I do not profess to know much about the latest improvements that have been made in connection with that process ; but 1 do know that the ordinary chlorinating process, such as that in use some time ago at Sandhurst, Victoria, would not suit our requirements. As a bullion extractor from iron pyrites, sulphurets, and concentrates generally, it was very successful, but ours is not a Concentrating ore, and I do not think it .would

have the desired effecfc when dealing with silica, with which our precious metals are associated. Ib is stated, however, that an Auckland gentleman who returned recently from Australia has secured the patent rights of a process, of which chlorination will form a part, that has already been proved to be equal to the ex ti action of at least 90 per cent, of the bullion value of local ore, at a cost of about 40.s per ton, and that a plant on this principle will bo erected at Wai hi early in the ensuing spring. C : Before leaving, will you be good enough to inform me how you arrive at the conclusion that this barren looking ore of yours' contains either gold or .silver in remunerative quantities without the assistance of an assay plant ? M. :It is very easily done. 1 take this piece of stone, which does not exhibit any sign of either gold or silver, and I cover it over with a light coating of carbonate of soda, then place it in the smithy fire and subject it to an intense heat for ten or lifteen minutes, after which I take it out, and, if it be rich, its siuface will be covered with globules of silver or g-lobulcs of silver and gold, as the case may be ; but you must be very careful about the temperafcme. If the heat is not &tron» enough, the globules won't appear, and then again, if the heat is too intense, the silver will simply be lost in the lire, and you will not get the desired information. In any case, however, it is best to employ the services of a competent assayer, "\\ ho will tell you what your ore is really worth, and if that system had been introduced here ten years ago it would have saved the speculating public some thousands of pounds, and this would bo a nourishing place to-day.