William Crookes

The De Beers Consolidated Mines, Limited, was founded in 1888, mainly through the genius of the late Cecil John Rhodes, for the purpose of acquiring all-important diamond-mining interests in the Kimberley area and thereby controlling the output. The two richest mines, Kimberley and De Beers, have been actively worked ever since, and have been the main contributors to an output which now realises over five millions sterling annually. Dutoitspan Mine was completely closed down, and practically the whole of Bultfontein was kept idle for many years; but with a view to the requirements of the future and the marked increase in the demand for diamonds, notwithstanding the steady rise in prices that has taken place, both these mines have now been equipped for underground working on a grand scale. The youngest of the De Beers group of mines is the Wesselton, which was discovered in 1890 by the late Mr. H. A. Ward, and soon afterwards purchased by Mr. Rhodes on behalf of the Company. The mine is now being worked opencast on a magnificent scale and has largely exceeded original expectations (Fig. 5). The success of the consolidation is proved by the fact that since it was brought about £22,000,000 have been paid in dividends to the shareholders, and it is roughly estimated that 40,000,000 carats of diamonds have been produced of a total value of eighty millions.

To face p. 34.

At the four mines about 8000 persons are daily employed, namely, 1500 whites and 6500 blacks. The wages are, whites, £5 or £6 a week; blacks, underground, 4s. to 5s. a day, and aboveground, 21s. a week.

The Compound System

With gems like diamonds, where so large an intrinsic value is concentrated into so small a bulk, it is not surprising that robbery has to be guarded against in the most elaborate manner. The Illicit Diamond Buying (I.D.B.) laws are very stringent, and the searching, rendered easy by the “compounding” of the natives—which I shall describe presently—is of the most drastic character (Fig. 6). It is, in fact, very difficult for a native employee to steal diamonds; even were he to succeed, it would be almost impossible to dispose of them, as a potential buyer would prefer to secure the safe reward for detecting a theft rather than run the serious risk of doing convict work on the Cape Town Breakwater for a couple of years. I heard of a native who, secreting a diamond worth several hundreds of pounds, after trying unsuccessfully to sell it, handed it back to the manager of his compound, glad to get the sixpence a carat to which he was entitled. Before the passing of the “Diamond Trade Act” the value of diamonds stolen reached nearly one million sterling per annum.

A “compound” is a large enclosure about 20 acres in extent, surrounded by rows of one-story buildings of corrugated iron. These are divided into rooms holding each about twenty natives. A high iron fence is erected around the compound, 10 feet from the buildings. Within the enclosure is a store where the necessaries of life are supplied to the natives at a reduced price, wood and water being provided free of charge. In the middle is a large swimming-bath, with fresh water running through it. The rest of the space is devoted to recreation, games, dances, concerts, and any other amusement the native mind can desire. I have to thank the superintendents of the respective compounds, who spoke all the native dialects, for their kindness in showing us round, and suggesting dances and concerts, got up at ten minutes’ notice, for the benefit of my camera. The dancing was more of the character of attitudinising and marching to a monotonous tum-tum, the “orchestra” consisting of various-sized drums and what they call a piano—an octave or so of tuned slabs of wood held in order on stretched strings and struck with a wooden hammer. The native music as a rule is only marking time, but I have heard musical melodies accompanying some of their songs. In case of accident or illness there is a well-appointed hospital where the sick are tended. Medical supervision, nurses, and food are supplied free by the Company.

In the compound are to be seen representatives of nearly all the picked types of African tribes. Each tribe keeps to itself, and to go round the buildings skirting the compound is an admirable object-lesson in ethnology. At one point is a group of Zulus; next we come to Fingoes; then Basutos; beyond come Matabele, Bechuanas, Pondos, Shangains, Swazis, and other less-known tribes, either grouped or wandering around making friendly calls.

The clothing in the compound is diverse and original. Some of the men are evident dandies, whilst others think that in so hot a climate a bright-coloured handkerchief or “a pair of spectacles and a smile” is as great a compliance with the conventions of civilisation as can be expected.

The natives are not interfered with in their various amusements, always provided they do not make themselves objectionable to their neighbours. They soon learn that tribal animosities are to be left outside the compound. One Sunday afternoon my wife and I walked unattended about the compound, almost the only whites present among 1700 natives. The manners of the fold were so friendly, and their smiles so cordial, that the idea of fear vanished. At one part a Kafir was making a pair of trousers with a bright nickel-plated sewing-machine, in which he had invested his savings; next to him a “boy” was reading from the Testament in his own language to an attentive audience; in a corner a party were engaged in cooking a savoury mess in an iron pot; further on the orchestra was tuning up and Zulus were putting the finishing touches to their toilet of feathers and beads. One group was intently watching a mysterious game. It is played by two sides, with stones and grooves and hollows in the ground, and appears of most absorbing interest. It seems to be universal throughout Africa; it is met with among the ruins of Zimbabwe, and signs of it are recorded on old Egyptian monuments. I wanted to learn it, and an intelligent Zulu player offered to teach it to me in a few minutes. Captain Dallas, however, with a more accurate opinion of my intelligence than my friend the Zulu, assured me it would take months before I could begin to know anything about it. He had tried for years and could make nothing of it.

They get good wages, varying according to occupation. The work is appreciated, and there are always more applicants than can be accepted. On entering, the restrictions to which they must submit are fully explained, and they are required to sign for three months at least, during which time they must not leave the compound or mine. A covered way and tunnel lead the workers underground to the down shaft, while those working on the depositing floors go and come under guard. It is seldom that a man does not return once he has lived the life in the compound; some come again and again for years, only leaving occasionally to spend accumulated savings. The most careful men save money, and carry it at intervals to the superintendent to keep for them. Occasionally they ask to look at their savings, which may amount to £30 or £40, accumulated by driblets. They are ignorant of savings banks or interest, and are content if they see their own money in the original rags and papers. The Kafir, on demand, must behold his coins just as he handed them in, wrappings and all. Sometimes the superintendent will have as much as £1000 of savings in his care.

On leaving, the men generally draw all their savings, and it is not uncommon for a grateful Kafir to press £2 or £3 on Captain Dallas in recognition of his trouble. They are astonished when their offerings are declined; still more so when it is explained that if they would put their savings in a bank they would have a few extra pounds given to them for the privilege of taking care of it.

A shrewd young Pondo, who had been coming year after year, applied for some of his savings, and gave as a reason that he wanted to buy a wife. “But you said the same thing last year,” replied Captain Dallas; “I hope nothing has happened.” “No,” said the man; “one wife, she quarrel with me; two wives, they quarrel with each other; me peace!”

Underground Workings

In the face of constant developments I can only describe the system in use at the time of my own visits in 1896 and 1905. Shafts are sunk in the solid rock at a sufficient distance from the pipe to be safe against reef movements in the open mine. In 1903 the rock shafts in the De Beers and Kimberley Mines reached depths of 2076 and 2599 feet respectively. Tunnels are driven from these shafts at different levels, about 120 feet apart, to cross the mine from west to east. These tunnels are connected by two other tunnels running north and south, one near the west side of the mine and one midway between it and the east margin of the mine. From the east and west tunnels offsets are driven to the surrounding rock. When near the rock the offsets widen into galleries, these in turn being stoped on the sides until they meet, and upwards until they break through the blue ground. The fallen reef with which the upper part of the mine is filled sinks and partially fills the open space. The workmen then stand on the fallen reef and drill the blue ground overhead, and as the roof is blasted back the debris follows. When stoping between two tunnels the blue is stoped up to the debris about midway between the two tunnels. The upper levels are worked back in advance of the lower levels, and the works assume the shape of irregular terraces. The main levels are from 90 to 120 feet apart, with intermediate levels every 30 feet. Hoisting is done from only one level at a time through the same shaft. By this ingenious method every portion of blue ground is excavated and raised to the surface, the rubbish on the top gradually sinking and taking its place.

The scene below ground in the labyrinth of galleries is bewildering in its complexity, and very unlike the popular notion of a diamond mine (Fig. 7). All below is dirt, mud, grime; half-naked men, dark as mahogany, lithe as athletes, dripping with perspiration, are seen in every direction, hammering, picking, shovelling, wheeling the trucks to and fro, keeping up a weird chant which rises in force and rhythm when a greater task calls for excessive muscular strain. The whole scene is more suggestive of a coal mine than a diamond mine, and all this mighty organisation, this strenuous expenditure of energy, this costly machinery, this ceaseless toil of skilled and black labour, goes on day and night, just to win a few stones wherewith to deck my lady’s finger! All to gratify the vanity of woman! “And,” interposed a lady who heard this remark, “the depravity of man!”

The Depositing Floors

Owing to the refractory character of blue ground fresh from the mines, it has to be exposed to atmospheric influences before it will pulverise under the action of water and mechanical treatment.

From the surface-boxes, into which the blue ground is tipped when it reaches the top of the main shaft, it is transferred to side-tipping trucks and sent to the depositing floors by means of endless wire-rope haulage. The speed of the haulage varies from 2½ to 4 miles per hour. The trucks are counted automatically as they are sent to the floor by a reciprocating engine-counter placed on a frame near the tramline.

The depositing floors are prepared by removing the bush and grass from a fairly level piece of ground; this ground is then rolled smooth and hard. The floors extend over many square miles of country and are surrounded by 7-foot barbed wire fences, vigilantly guarded day and night. The De Beers floors, on Kenilworth, are laid off in rectangular sections 600 yards long and 200 yards wide, each section holding about 50,000 loads. The ground from the Kimberley Mine is the softest and only needs a few months’ exposure on the floors; the ground from De Beers is much harder and requires at least six months’ exposure, while some ground is so hard that it will not disintegrate by exposure to the weather under one or two years. The De Beers Mine contains a much larger quantity of this hard blue ground than the other mines, and in order to save the loss of time consequent on keeping an enormous stock of blue constantly on the floors, it has recently been decided to pass the harder and more refractory stuff direct from the mine through crushing mills.

For a time the blue ground remains on the floors without undergoing much alteration. But soon the heat of the sun and moisture produce a wonderful effect. Large pieces, hard as ordinary sandstone when taken from the mine, commence to crumble. At this stage the winning of the diamonds assumes more the nature of farming than mining. The ground is frequently harrowed and occasionally watered, to assist pulverisation by exposing the larger pieces to atmospheric influences. The length of time necessary for the ground to weather before it becomes sufficiently pulverised for washing depends on the season of the year and the amount of rain. The longer the ground remains exposed the better it is for washing.

It is curious to note that there is a marked difference in the rapidity of disintegration of the blue ground in each of the four mines. The longer the exposure, the more complete the pulverisation and the better for washing. Under normal conditions soft blue ground becomes sufficiently pulverised in from four to six months, but it is better to expose it for a longer period, even for a whole year.

Washing and Concentrating Machinery

After the blue ground has been weathered for a sufficient time, it is again loaded into trucks and hauled to the crushing machinery (Fig. 8). The first or “comet” crushers reduce the ground so that it will pass into hoppers and thence into revolving cylinders covered with perforated steel plates, having holes 1¼ inches in diameter which separate the finely crushed from the coarse pieces.

Pieces larger than 1¼ inches pass out of the end of the cylinders and fall upon a conveyor belt, which takes them to the end of the machine—these pieces are mostly waste rock which is found in the blue ground.

The fine ground which passes through the holes in the cylinder, together with a plentiful current of water, flows into the washing pans. These pans are of iron, 14 feet in diameter, furnished with ten arms each having six or seven teeth. The teeth are so set as to form a spiral, so that when the arms revolve the teeth carry the heavy deposit to the outer rim of the pan, while the lighter material passes towards the centre and is carried from the pan by the flow of water. The heavy deposit contains the diamonds. It remains on the bottom of the pan and near its outer rim. This deposit is drawn off every twelve hours by means of a broad slot in the bottom of the pan. The average quantity of blue ground passed through each pan is from 400 to 450 loads in ten hours. The deposit left in each pan after putting the above number of loads through amounts to three or four loads, which go to the pulsator for further concentration.

About 14 per cent of all the ground sent to the depositing floors is too hard to weather, so of late years crushing and concentrating plant has been erected to deal effectually with the hard lumps, thus saving the great lock-up of capital consequent on letting them lie on the floor a year or two.

The hard lumps being hauled to the upper part of the machine, are tipped into bins, whence they pass to crushing rollers which so reduce them that they will pass through a ring two inches in diameter. The coarse powder is screened through revolving cylinders having ½-inch and 1¼-inch perforations. The stuff passing through the finer holes goes to the finishing mill, while the coarser stuff goes to smaller crushers. Before the coarse lumps are re-crushed they pass over revolving picking tables, where any specially large diamonds are rescued, thus preventing the risk of breakage. From the picking tables the ground is scraped automatically into two sets of rolls, and the pulverised product screened again and graded into three sizes. The finest size, passing a ½-inch screen, goes to the washing pans, and the two coarser sizes to jigs. Large diamonds which have been separated from their envelope of blue are retained in the jig. The ground still holding the smaller diamonds passes out of the end of the jig and then through a series of rolls, screens, and jigs until the diamantiferous gravel is drawn from the bottom jigs into locked trucks running on tramways to the pulsator for further concentration and sorting.

The pulsator is an ingeniously designed but somewhat complicated machine for dealing with the diamantiferous gravel already reduced one hundred times from the blue ground, the pulsator still further concentrating it till the gravel is rich enough to enable the stones to be picked out by hand. The value of the diamonds in a load of original blue ground being about 30s., the gravel sent to the pulsator from the pans, reduced a hundredfold, is worth £150 a load. Stuff of this value must not be exposed to risk of peculation.

The locked trucks are hoisted by a cage to a platform, where they are unlocked and their contents fed into a shoot leading to a cylinder covered with steel sieving with holes from ¹/₁₆ to ? of an inch in diameter. The five sizes which pass through the cylinder flow upon a combination of jigs, termed at the mines the pulsators. The bottoms of the jigs are covered with screens, or sieving, the meshes of which are a little larger than the holes in the revolving cylinder immediately at the back of them.

Over each screen is spread a layer of bullets to prevent the rich deposit from passing too rapidly through the screens. The jigs themselves are stationary, but from below an intermittent stream of water passes in rapid pulsations with an up and down movement. This pulsation keeps the diamantiferous gravel constantly moving—“alive” is the expressive word used—and tends to sort out the constituents roughly according to their specific gravity, the heavier particles working to the bottom and the lighter material washing off by the flow of water and passing into trucks, whence it is carried to the tailings heap. The heavier portions, by the up and down wash of the water, gradually work their way under the bullets and pass through the screens into pointed boxes, whence the heavy concentrates are drawn off upon endless belts. These convey their precious load to small elevators by means of which the concentrates are lifted into hoppers from which they are fed upon shaking tables.