South Africa and the Transvaal War, Vol. 8 (of 8) / South Africa and Its Future

by Unknown

CYANIDE WORKS (NEW COMET MINE) AT JOHANNESBURG
The tailings are run into the huge vats, and the cyanide of potassium a deadly poison percolates through, and carries off the gold in solution.
Photo by Barnett & Co., Johannesburg

Section of a Gold Mine. (Photo by Horace W. Nicholls, Johannesburg)

These beds lie in series, that particular one which contains most of the gold being called the Main Reef series, comprising the Main Reef proper and a number of subordinate reefs or bands. The thickness of the Main Reef is from 3 to 12 feet, that of the Main Reef Leader 3 feet on the average, and the South Reef thinner than the latter, but having a richer gold contents than either. These are the beds chiefly worked, the gold being disseminated throughout the matrix mainly in crystals, visible gold being only occasionally seen, but in fairly regular quantities, so that the results of working, whether in the richer or poorer reefs, are capable of being accurately forecasted. The knowledge of the nature and extent of the beds has only gradually been brought together, and is still incomplete in parts even for the 15 miles section of the Rand which has been longest under working, and discoveries are of almost daily occurrence extending the sum of information regarding their composition and incidence. In the section situated between the Langlaagte Estate Mine in the west and the New Comet in the east, one profitable mine after another follows almost without a break. The eastern and western extensions are, for the main part, still terra incognita; but the several mines scattered along their stretch have confirmed the identity and value of the formation, which is held by experts to warrant the belief in the existence of wealth even exceeding the Rand proper.

Knowledge as to the depth to which the reefs descend has been slowest in accumulating. When the outcrops were first worked in the central section, it was believed that there was little or no gold in the lower levels. Since 1898, however, deep and yet deeper depths have been explored, especially in following the richer reefs, and always with the similar result of meeting with the same, or a superior, grade of ore contents peculiar to the higher sections of the particular reef, so that the inference is strengthened to certainty that profitable exploitation is only limited to the ultimate depth at which modern mining can be carried on. The problem, therefore, is one for the engineers; for, apart from the increased temperature in the lower levels, which can be met by roomier shafts, and the occurrence of water, which is likewise capable of being dealt with, the only difficulty to be met with is that concerned with the hoisting appliances for such enormous depths. So recently as May last the London Chamber of Mines, and more recently the Johannesburg Association of Mining Engineers, were engaged on the solution of this question. It is needless to anticipate the results of their deliberations, the point turning upon the choice betwixt two systems, only so far as to state that means for solving the difficulties of the task are considered to be available, at least, to such depths as 5565 feet on the slope, and that the results of mining at these great depths can be made to show a substantial profit. It may be added, however, that in consequence of the increased cost to reach the ore, the need for the utmost reduction of working costs becomes paramount.

The circumstances of gold-mining on the Rand have, therefore, features quite distinct from those of quartz-reef, alluvial, or other kinds of mining, and approximate to those of coal winning, especially in the matter of the depth and regularity of the conglomerate formation. Its peculiarities have created a method of mining, the outcome of costly experiment, experience, and skill, which will remain a lasting asset to future ages.

The future gold production of the Rand mining industry is a subject which enchains the attention alike of the investor and the curious. In approaching the subject of the unexploited gold contents of the banket formation, figures are handled which simulate the fabulous, and almost excuse the disbelief with which all such estimates are received in some quarters. Confirmation of the approximate correctness of the computations may, however, be obtained in two ways: firstly, from the past yield of the gold-fields in the seventeen years since their start; and secondly, from the verification of former prognostications which subsequent outputs have furnished. So far as regards the former, the fact of the production of £81,000,000 of gold since the start of the industry up to now, under well-known circumstances is, in the first place, proof positive that the gold exists; and, in the second, affords inferential grounds for assuming that, given at all similar circumstances, mining operations will yield like results. This is, of course, taking the lowest ground, for it is indubitable that the circumstances will not be alike, but vastly improved, in which case the value of the results will be proportionately enhanced. As to the confirmation which results from the verification which later outputs have furnished, both of the trustworthiness of the bases on which former forecasts were made and of the prognostications themselves, there may be instanced the forecasts of such early computators as Mr. Hamilton Smith, Mr. C. D. Rudd, and others. The former, in 1892, in a report on the future production of the Rand fields, made by request of Messrs. Rothschild, adventured an opinion which is worth quoting textually. He said: “With the active and energetic men who have this industry in hand, and always supposing that the foregoing theories be correct, in three or four years from now the producing power of the mines and their reducing works will, I think, be increased to an output of five or six million tons of ore per annum, worth a gross yield of over £10,000,000. At this rate the available supply of ore, as conjectured above, will last for more than thirty years.”

As an actual fact, in four years from the time of his writing the above, the Rand gold yield from 69 companies working amounted to 5,325,355 ozs., the total production being of the gross value of £10,583,616; so that, far from his estimate being too sanguine or exaggerated, it was a literal forecast of the actuality. He subsequently expressed the opinion that the full producing power of the Rand would be reached by the end of the century, when the output might be expected to exceed £12,500,000 per annum. As a matter of fact the total value of gold produced in the Transvaal in 1898 was over £15,000,000, most of which came from the Rand, and, had mining operations in 1899 not been interrupted by the war, the output in that year would have reached to over £18,000,000. Mr. Smith based his estimate on a working depth of 5200 feet, and on an area of the reef only 11 miles in extent, but since his time deep mining has been successfully prosecuted to 7000 feet. Inference and analogy, therefore, both afford strong support to the correctness of estimates, based on the results of past working, of the future gold contents of the Witwatersrand reefs, which estimates, as appears, are more likely to be under-reckoned than otherwise, from the sheer immensity of the subject, and from the necessarily imperfect knowledge of the potentialities of so huge a problem.