Deep Down, a Tale of the Cornish Mines

by R. M. Ballantyne

Being finally cleansed from all its impurities, our mass of tin bears more resemblance to brown snuff than to metal. An ignorant man would suppose it to be an ordinary earthy substance, until he took some of it in his hand and felt its weight. It contains, however, comparatively little foreign substance. About seventy per cent of it is pure tin, but this seventy per cent is still locked up in the tight embrace of thirty per cent, of refuse, from which nothing but intense fire can set it free.

At this point in the process, our mass of tin leaves the rough hand of the miner. In former days it was divided among the shareholders in this form—each receiving, instead of cash, so many sacks of tin ore, according to the number of his shares or “doles,” and carrying it off on mule or horse back from the mine, to be smelted where or by whom he pleased. But whether treated in this way, or, as in the present day, sold by the manager at the market value, it all comes at last to the tin-smelter, whose further proceedings we shall now follow, in company with Oliver and his friend.

The agent of the smelting company—a stout, intelligent man, who evidently did “knaw tin”—conducted them first to the furnaces, in the neighbourhood of which were ranged a number of large wooden troughs or bins, all more or less filled with tin ore. The ore got from different mines, he said, differed in quality, as well as in the percentage of tin which it contained. Some had much iron mixed with it, in spite of all the washings it had undergone; some had a little copper and other substances; while some was very pure. By mixing the tin of different mines, better metal could be procured than by simply smelting the produce of each mine separately. Pointing to one of the bins, about three yards square, he told them it contained tin worth 1,000 pounds. There was a large quantity of black sand in one of the bins, which, the agent said, was got by the process of “streaming.” It is the richest and best kind of tin ore, and used to be procured in large quantities in Cornwall—especially in ancient times—being found near the surface, but, as a matter of course, not much of that is to be found now, the land having been turned over three times in search of it. This black sand is now imported in large quantities from Singapore.

The agent then conducted his visitors to the testing-house, where he showed them the process of testing the various qualities of tin ore offered, to the House for sale. First he weighed out twenty parts of the ore, which, as we have said, resembled snuff. This, he remarked, contained about five-sixths of pure tin, the remaining one-sixth being dross. He mixed it with four parts of fine coal dust, or culm, and added a little borax—these last ingredients being intended to expedite the smelting process. This compound was put into a crucible, and subjected to the intense heat of a small furnace for about twenty minutes. At the end of that time, the agent seized the crucible with a pair of tongs, poured the metal into an iron mould, and threw away the dross. The little mass of tin thus produced was about four inches long, by half an inch broad, and of a dull bluish-grey colour. It was then put into an iron ladle and melted, as one would melt lead when about to cast bullets, but it was particularly noteworthy here, that a very slight heat was required. To extract the metal from the tin ore, a fierce heat, long applied, was necessary, but a slight heat, continued for a few minutes, sufficed to melt the metal. This remelted metal was poured into a stone mould, where it lay like a bright little pool of liquid silver. In a few seconds it solidified, retaining its clear purity in all its parts.

“That,” said the agent, “is tin of the very best quality. We sell it chiefly to dyers, who use it for colouring purposes, and for whom no tin but the best is of any use. I will now show you two other qualities—namely, second and inferior.”

He went to a small cupboard as he spoke, and took therefrom a small piece of tin which had already gone through the smelting process in the crucible above described. Melting this in the ladle, he poured it into the mould, where it lay for a few moments, quite bright and pure, but the instant it solidified, a slight dimness clouded its centre.

“That,” explained the agent, “is caused by a little copper which they have failed to extract from the tin. Such tin would not do for the dyers, but it is good for the tin-plate makers, who, by dipping thin sheets of iron into molten tin, produce the well-known tin-plates of which our pot-lids and pans, etcetera, are manufactured. This last bit, gentlemen,” he added, taking a third piece of tin from the cupboard, “is our worst quality.”

Having melted it, he poured it into the mould, where it assumed a dull, half-solid appearance, as if it were a liquid only half frozen—or, if you prefer it, a solid in a half molten state.

“This is only fit to mix with copper and make brass,” said the agent, throwing down the mould. “We test the tin ore twice—once to find out the quantity of metal it contains, and again to ascertain its quality. The latter process you have seen—the former is just the same, with this difference, that I am much more careful in weighing, measuring, etcetera. Every particle of dross I would have collected and carefully separated from any metal it might contain; the whole should then have been reweighed, and its reduction in the smelting process ascertained. Thus, if twenty parts had been the weight of tin ore, the result might perhaps have been fourteen parts of metal and six parts of dross. And now, gentlemen, having explained to you the testing process, if you will follow me, I will show you the opening of one of our furnaces. The smelting-furnace just shows the testing process on a large scale. Into this furnace, six hours ago,” he said, pointing to a brick erection in the building to which he led them, “we threw a large quantity of tin ore, mingled with a certain proportion of culm. It is smelted and ready to be run off now.”

Here he gave an order to a sturdy man, who, with brawny arms bared to the shoulders, stood close at hand. He was begrimed and hairy—like a very Vulcan.