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Volume 20, 1887
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Art. XLIV.—Minerals at Nelson.

[Read before the Nelson Philosophical Society, 6th February, 1888.]

In the Nelson District we have but little agricultural land, but we have an immense tract of mineral land, of the value of which we have not, as yet, any idea. If we are to prosper, it must be by the development of mining and manufactures; and for both of these industries we have natural advantages, if we will only make use of them. The day is past when we could by the primitive means of dish, cradle, or sluice-box, take out of the creeks and gullies the gold, which the action of air and water had separated from the matrix, and concentrated there. We have now to win the minerals from their lodes, and we must study the best way to discover these, and extract the valuable metals economically when they are found. If I can contribute anything about this matter that will interest you, I am sure I shall be very happy to do so; and if it only has the effect of directing attention to some of the more obscure forms of the

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valuable metals existing in our district it will serve a useful purpose.

The subject is such an extensive one, that it is difficult to know where to begin: and perhaps I cannot do better than first show you some ores, giving some particulars about them which will illustrate the usefulness of a School of Mines, and, secondly, the need of a central reduction works, and the natural capabilities of the Nelson District for such an establishment.

The first piece of ore I will show you really belongs to the order of grey copper ores, but having such a high percentage of silver is called a silver ore. It comes from Richmond Hill, Collingwood, and was named by Dr. Hector “Richmondite,” as it was a new form of grey copper. From the analysis made at the Government Laboratory, Wellington, this ore is composed of the following eight minerals:—

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Sulphides of Lead 36.12
Antimony 22.20
Bismuth Traces
Copper 19.31
Iron 13.59
Zinc 5.87
Silver 2.39 (390 oz.)
Manganese .52

This was taking the average across the vein: but some of it assayed as high as 1,792 oz. of silver to the ton. The ore occurs in a gneiss rock, the adjoining rocks being all of a silver-bearing character; and if we geologically compare Richmond Hill with the principal silver-bearing districts of the world, we shall be surprised how similar it is, in the most essential particulars. We have here a class of country peculiarly silver bearing, in whatever part of the world it may be found; and we have also very rich specimens of silver, nickel, and associated minerals found in this class of country. Nature has done much in thus showing us the strong indications of hidden wealth: but we lack the capital, the energy, and knowledge of its value to follow it up. Gold in its metallic state has more attraction for the public. It is more simple; for when the stone is crushed the product is readily saleable anywhere. It has, moreover, been first in the field, and has attracted public attention to the exclusion of nearly all other minerals. In California the grand silver deposits were passed over for years, and the dull, unattractive-looking ore was thrown by as worthless in the search after gold. Thousands passed over it, little thinking of the wealth they were treading under foot. May we not be doing the same thing now? If we consider that there are about seventeen

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varieties of silver ore, totally different in appearance from each other; that the silver may be in one or several of these forms in the same lode; that it may occur as a valuable constituent of the ore of any other mineral; and that, by the action of air or water, all or any of these may alter their chemical nature and appearance altogether, we shall not be surprised that valuable silver deposits are often overlooked and neglected.

The specimen of richmondite you have just seen shows how silver may be combined with other minerals. It is a very rich specimen of silver ore, yet the proportion of silver is only 2.39, to 97.61 of other minerals; but, under favourable circumstances, a tenth, or less, of this percentage would make a valuable silver mine.

I will now show you some silver buttons that I obtained some years ago from 200 grains of the richmondite. They represent from 260 ozs. to 770 ozs. to the ton of ore.

I will next show you some silver ore that does not belong to New Zealand, but comes from the “Sunny Corner,” New South Wales, from a mine that produced 4 ¼ tons of refined silver in three months. If you compare it with this second specimen you will see that there is not much in its appearance to show that it is a valuable silver ore, while the other is only a worthless piece of ironstone; yet analysis shows this to be the case.

Scattered all over our country is material similar in appearance to those specimens you have just seen; and the great question we want to solve is: Are they all worthless? or do some of them, like the “Sunny Corner,” contain valuable metals, in an obscure form, hidden within them? The only way to ascertain this is to have them analysed, and this should be done free—that is, at the country's expense—as all the people of New Zealand will reap the benefit of any discovery that is made. Many do not take into consideration how much our interests as a community are bound together, and think that having assays made free would be giving a direct benefit to miners only. This is a short-sighted view to take! The miner or explorer, by expense, labour, and hardship in searching for and carrying specimens over miles of weary hill and dale, quite earns any extra benefit he may get through having assays made free. As showing the difficulties often attending the collection of specimens, I will mention a case which occurred to a friend and myself five or six years ago. We had a long trip over some of the roughest mountains between Nelson and the West Coast, and had collected specimens of rocks, minerals, etc., on our way. After carrying these twelve hours a day for nearly three weeks, we had to throw them away to lighten our loads, and push on for food, as we had nothing whatever to eat, and had had but very little for the

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previous four days. We were not out looking for minerals, but took them in our way, and should not have felt inclined to pay several pounds to have had them assayed if we had brought them in, although we certainly should have had them analysed if free of cost, and the information might have been of value to the country, if not to us particularly. I feel sure some of the country we crossed is tin-bearing; and if the specimens from there showed the presence of tin, they would, by proving that valuable mineral to exist there, have induced prospectors to search for the lode containing it.

The next specimen for you to see is from the “Union” mine, in the Waihi District, and contains gold and silver to the value of about £43 per ton. I will quote what Professor Black says of these ores, as it clearly shows a need of analytical knowledge in finding them, and a metallurgical knowledge to work them successfully. In his report, he says:— “Most of the gold also in the silver-bearing ore exists as a blackish sulphide of gold, probably in combination with the sulphide of silver, and thus escapes the notice of the miner who is prospecting on the old lines. It is only when gold and silver are brought out, either by the fire assay process, or by the wet chemical processes, that the value of the stone is known. Much of the stone on the Waihi and Karangahake, containing gold and silver worth from £10 to £100 per ton of stone, has been overlooked for want of a little of this kind of knowledge.” You will notice there is nothing attractive-looking about that piece of stone, and few would give a second glance at it. Yet those dark patches are rich in gold and silver, although not in the bright particles we expect to see them.

The next specimen I have to show you is from Te Aroha, the southern extremity of the Thames Goldfield. The mines here are situated about two-thirds up the mountain of Te Aroha, and the expense of getting stone from the mines to the battery at Waiorongomai, together with the loss of gold by the ordinary process of treating the stone, has prevented this field paying as well as it should. The dark portions of the stone are the rich ones; and a strong magnifying glass will show that the discoloration is mainly caused by fine particles of gold, which, like all the gold in this district, is very much alloyed with silver. These specimens show that, although “all is not gold that glitters,” still a great deal that does not glitter may be gold, and that we cannot from its appearance judge of the value of an ore. It may be thought that I lay too much stress on the necessity of assays being made free of cost: but consider the vast extent of mineral country that we have; the difficulties of travelling and searching for minerals, from the roughness of the country, and the growth on it; and it will be seen that the few men who are engaged professionally prospecting for them are like drops

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of water in the ocean. They have their effect, but it is very slight. These cannot afford to pay to have assays made of every mineral they may find, so confine their prospecting to the more easily recognised gold. By having assays made free, not only are these encouraged to search for other minerals, but it developes another class of amateur geologists, so to call them, who are interested in knowing what any ore they may find contains. This class greatly increases the number of explorers and searchers, and some of the most valuable mineral deposits have been discovered through them. Davies, in his “Metalliferous Minerals and Mining,” says: “As a matter of experience, we have seen that many of the richest mines have been discovered by accident: the wayfarer, resting in the wilds of the Saxon forest; or the muleteer, in scrambling after his mule in Brazil. The curiosity excited by the great weight of the stone in California Gulch led to the discovery of carbonate of lead.” These are a few examples of what at first sight seems to be the accidental discovery of mines. But such discoveries were accidental only by reason of the previous ignorance or indifference of the dwellers in the land; for in each of the above illustrations there were natural indications which would make it plain to intelligent seekers that valuable minerals were near. The establishment of a School of Mines would greatly assist in removing ignorance and indifference; for with more knowledge would come greater interest, and to young men especially such instruction must be useful. I believe it would give to mining a truer and higher tone than it has at present, when miners are miners if it enables scrip-holders to sell their scrip at a fictitious value; and the study of scrip-holders now is not so much what is best for the mine, as what will enable them to sell their scrip at a profit. This degrades mining from an honest speculation to a kind of fraudulent gambling, very injurious to the mining industry.

Before entering upon the advantages we possess in the Nelson District for treating ores which require to be smelted to obtain the valuable metals they contain, it may be as well to show what is required to do so successfully. Briefly, we may say that these are accessibility, cheap fuel, flux, and power. We can get an instructive lesson from La Monte's smelting at the Thames last year, which, although a failure—in so far that it did not do what he stated that it would—shows forcibly several causes of failure. La Monte engaged to save 90 per cent. of the gold and silver in the ore, at a cost of £2 per ton; but he did not succeed in saving that percentage, and it cost £6 15s. per ton for treatment. Possibly La Monte had been used to ores which contained the necessary flux in themselves, and he did not calculate the cost and quantity that the quartz ores he had to treat would require; hence we find that

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for flux alone the cost came to nearly 30s. per ton of ore, out of the 40s. for which he was to treat it; and even then he did not use enough to save the percentage he engaged to do. The proportion of ore to flux and fuel in such ores may be taken roughly as one to three; so that it is cheaper to take the ore to the flux and fuel than the reverse.

At the Parapara, Collingwood, there are immense deposits of ironstone and crystalline limestone, both of first-class quality. They are close to deep water in a very central position, bordering on the Straits, and so in the line of vessels; fuel and water-power are cheaply and easily obtainable. If we take the cost of flux and fuel at the Thames for the 181 tons of ore treated there, and compare it with the cost of the same quantities at the Parapara, we shall see what a difference there would be in the cost of treatment. I take the following quantities and prices for the Thames from the report of the Directors:—

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Tons. £ s. d.
Iron Ore 320 at 5/- 240 0 0
Lime 59 " 7/6 22 2 6
Grey Coke 56 " 59/- 165 4 0
Gas Coke 61 " 26/- 81 3 0
Coal 15 " 31/6 22 12 6
£531 2 0

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Tons. £ s. d.
Iron Ore 320 at 2/6 40 0 0
Lime 56 " 2/6 7 7 6
Grey Coke 56 " 40/ 112 0 0
Gas Coke 61 " 23/- 70 10 0
Coal 15 " 10/- 7 10 0
£237 0 6

A difference of £294, less the freight on the ore from the Thames to Parapara.

A great consideration in favour of having one central establishment where the materials required are cheaply obtained is, that the necessary appliances, skilled labour, and knowledge can be concentrated to treat any and all ores. This cannot be done with small scattered ones about the country; and the cost of treatment in the former would be much less per ton, besides the fact that the mixing of different ores is often necessary and generally beneficial. The opening of reduction works in a position available to all New Zealand, as this would be, would have a very useful and encouraging effect on mining. Ores of all kinds would then have a marketable value, and it would do away with the present uncertainty of the working value of an ore. The length of time a mine may last is too uncertain to warrant the expenditure necessary for treating the ores economically; and, although a mine may have a few or even a good many tons of good ore to treat, it is necessary that there should be a very large quantity proved before erecting furnaces, etc. The consequence of this is that much valuable ore is lost, because it is scattered about the country, a few tons here and a few tons there, not sufficient in any one place to put up the costly plant for, but which could be brought to a central

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establishment if such existed. A central reduction works would also have the advantage of not being dependent on any one mine, so that if some failed, others would be coming forward.

We know there is a great waste of gold from our quartz batteries, amounting to thousands of pounds annually. If the gold, etc., could be extracted at a reasonable price, or if the ore had a market value of so much per cent of the assay value, mine proprietors would soon and without much expense concentrate their tailings, until they contained a high percentage of bullion. This could then be treated or sold, and the product would add very considerably to the returns from many of the mines, and would make ground payable that is not so now on account of the loss of metal.

In the case of the Champion Copper Company, I think perhaps it would have answered their purpose better to have put up their smelting works at Parapara instead of at the mine, where they have to carry fuel and flux up, and then the copper down. Certainly, if there had been smelting works at the Parapara it would have made a great difference to them; for they could then have gone on proving their mine, and getting returns by sending their ore there to be smelted; and, if there had not been much profit while proving their mine, there would not have been much loss, and the proving would have been thorough. Now, after spending so much on machinery, they have a very promising but unproved mine; and the value of the plant depends entirely on the success of that one mine. The erection of the necessary works in a position so peculiarly adapted by Nature for economically treating ores would give a great impetus to mining, by enabling mine proprietors to get the working value of their product, and some return for their outlay while the work of prospecting was proceeding. It would lead to new lodes being found; some of those now abandoned being prospected and worked; and prevent the rash expenditure for machinery (in the expectation of early dividends) of money that should be spent in the ground. Thousands of pounds every year are completely thrown away in this manner, and mines abandoned—not because they have been proved worthless, but because all the money has been spent in machinery to treat ores that they have not the money left to win. The rich veins that will pay with the present wasteful treatment are few, compared to the poorer ones that would be remunerative with a proper system; and it is these that form the bulk of our mineral wealth. For instance, with quartz reefs, if we could not make less than 1 oz. of gold to the ton pay, the number of mines worked would be very few, we will say five; if ½ oz., perhaps twenty; but if a ¼ oz. could be made to pay, the proportionate number would be raised to 100. In minerals other than gold this is still more the case, as there are a number of elements for profit

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or loss, and it requires more knowledge and skill to make it a profit. Money, labour, and skill are expended to mine ores from the earth, and then they are treated in such a way that perhaps the greater percentage of the metal for which they were mined is lost.

The feeling of uncertainty as to what to do with an ore, if found, causes many good indications to be neglected. In Great Britain, nickel ore is worked at an average of 2.3 per cent, of nickel; in Spain, at 3.96; in Canada, a 9-inch deposit, at from 3 to 4 per cent.; and in Connecticut, a 12-inch vein, with a percentage of 2.2. The greater proportion of the nickel of commerce is derived from pyrrhotine. Yet on the Richmond Hill lease there is a vein larger than those mentioned, which, on the surface, gives 2.98 per cent, of nickel—and this has not excited enough interest even to cause it to be prospected. Mr. S. H. Cox says of this vein: “As nickel is extracted from this ore in New Jersey, United States, when only 3 per cent, is present, this should prove payable, if the lode is continuous and sufficiently large.” I mention this case, as it is characteristic of many others that will lie dormant until means are provided for their proper economical treatment in the Colony.

Briefly, the advantages of such works to mining would be that much valuable mineral now thrown away would be profitably saved; many mines, abandoned or undeveloped, would be prospected and profitably worked; and large sums of money now wasted for machinery on unproved mines would be saved.

I believe that smelting works would be a good investment, and could be profitably worked at the Parapara, if the requisite capital and knowledge were brought to bear on it. If the proprietors either treated the ore for so much per ton, or, perhaps still better, bought the various ores, giving such a percentage of the assay value as left them a sufficient margin of profit, a supply of ores would soon spring up, and they would practically have a monopoly of the business; for, as they could treat ores more cheaply than elsewhere, so they could give a better price for them. In many cases the by-products would of themselves give a good profit. The richmondite—even if we do not reckon the 36 per cent, of lead, or the 22 per cent, of antimony—is a good copper ore, and its 19 per cent, of copper should be a good product, in addition to the silver.

As most of the ores they would have to treat in New Zealand would be sulphides, they should be able to make sulphuric acid in treating them. This is an article much used for artificial manures and other purposes; and the colonial manufacture would have an advantage from the difficulty of transporting it. In England they import sulphide of iron from Spain for the sole purpose of making this acid from it. But in the Parapara District, sulphide of iron, containing from ½ dwt. up to as high

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as 3 to 4 ozs. of gold per ton, is plentiful; and I believe sulphuric acid could be made in quantity at a less cost there, than as at present, from the limited and precarious supply of sulphur from the volcanic region of the North Island.

We cannot afford to waste several valuable constituents of an ore, and mining will not progress in a satisfactory manner while we do. I believe that, by having the means of getting ores economically and properly treated in New Zealand, we would cause an interest in genuine mining highly beneficial to the whole Colony, and, if properly conducted, it would be a profitable investment. We have all the natural advantages for doing this in the Nelson District, if they were only utilised, and a first step towards this, I consider, is to make those advantages known.

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To illustrate Paper by E. Tregear.