How the great pipes were originally formed is hard to say. They were certainly not burst through in the ordinary manner of volcanic eruption, since the surrounding and enclosing walls show no signs of igneous action, and are not shattered or broken up even when touching the “blue ground.” It is pretty certain these pipes were filled from below after they were pierced and the diamonds were formed at some previous time and mixed with a mud volcano, together with all kinds of debris eroded from the rocks through which it erupted. The direction of flow is seen in the upturned edges of some of the strata of shale in the walls, although I was unable to see any upturning in most parts of the walls of the De Beers Mine at great depths.
The Kimberley Mine in Old Days
According to Mr. Paterson, who examined the diamond fields of Kimberley soon after their discovery, “Wherever the diamond is obtained perfect in form and smooth in finest smoothness of surface, without depression, hump, or twist of any kind, such diamonds were ever found in their own little moulds of finest limey stuff,[2] and as if such mould of lime had been a necessity to their perfect formation. And further, where the splinters of diamonds, or boarty stuff, were chiefly met by the diggers, there was much less presence of limey matter in the claim at the section of it where such broken or fragmentary diamonds were found; and that chiefly from among what the diggers termed ‘clay-ballast,’ or ‘burnt brick,’ were unearthed the bits or undeveloped crystals so plentiful at New Rush.”[3]
In the first days of diamond mining there was no idea that diamantiferous earth extended to any particular depth, and miners were allowed to dig holes at haphazard and prospect where they liked. When the Kimberley Mine was discovered a new arrangement was made, and in July, 1871, it was cut up into about 500 claims, each 31 feet square, with spaces reserved for about fifteen roadways across the mine. No person at first could hold more than two claims—a rule afterwards modified.
The following quotation from a description of a visit to Kimberley in 1872, by Mr. Paterson, taken from a paper read by him to the Geologists’ Association, gives a graphic picture of the early days of the Kimberley Mine:
“The New Rush diggings (as the Kimberley Mine was at first called) are all going forward in an oval space enclosed around by the trap dyke, and of which the larger diameter is about 1000 feet, while the shorter is not more than 700 feet in length. Here all the claims of 31 feet square each are marked out with roadways of about 12 feet in width, occurring every 60 feet. Upon these roadways, by the side of a short pole fixed into the roadway, sits the owner of the claim with watchful eye upon the Kafir diggers below, who fill and hoist, by means of a pulley fixed to the pole above, bucketful after bucketful of the picked marl stuff in which the diamonds are found.
“Many of the claims are already sunk to a depth of 100 feet, and still the diamonds continue to be found as plentifully as ever. From the roadway above the marl is carted away to the sorting-tables, outside the range of the diggings, among mounds of marl stuff which seem like little hills. Here, amidst such whirls of dust as are nowhere else seen, the marl stuff is pounded, sifted from the finest powder of lime and clay, and from the residue put on the sorting-tables, the diggers, with a piece of zinc 9 inches long by 4 inches in breadth, search out in the successive layers taken from the heap the precious gems. I need not tell you that the search is by no means very perfect, or that perhaps as many diamonds escape the digger’s eye as are discovered and taken out by him, but you will perhaps confess with me that their aptness in picking out the diamonds is by no means to be despised, when I tell you that in one six months from the date of opening New Rush diggings, little short of a million sterling in diamonds has been extracted from them. At close of day the diggers take daily stock of their finds, and between five and six o’clock in the afternoon are to be seen hundreds and hundreds moving through the main street of New Rush on visits to the tents of the buyers, seated behind their little green baize tables, with scales all ready, and bags of gold and silver and piles of banknotes, to buy the little gems.”
It may help to realise the enormous value of the Kimberley Mine if I say that two claims, measuring together 62 by 31 feet and worked to a depth of 150 feet, yielded 28,000 carats of diamonds.
The roadways across the mine soon, however, became unsafe. Claims were sunk 100 or 200 feet each side of a roadway, and the temptation to undermine roadways was not always resisted. Falls of road frequently took place, followed by complete collapse, burying mine and claims in ruin. At that time there were probably 12,000 or 15,000 men at work in the mine, and then came the difficulty how to continue working the host of separate claims without interference with each other. A system of rope haulage was adopted.