In the pulsator and sorting house most of the native labourers are long-sentence convicts, supplied with food, clothing, and medical attendance by the Company. They are necessarily well guarded. I myself saw about 1000 convicts at work. I was told that insubordination is very rare; apart from the hopelessness of a successful rising, there is little inducement to revolt; the lot of these diamond workers is preferable to life in the Government prisons, and they seem contented.
[Illustration: FIG. 10. DE BEERS DIAMOND OFFICE. 25,000 CARATS.]
[Illustration: FIG. 11. DE BEERS DIAMOND OFFICE. THE VALUATORS’ TABLE.
From the pulsator the diamonds are sent to the general office in Kimberley to be cleansed in a boiling mixture of nitric and sulphuric acids. A parcel of diamonds loses about half a part per 1000 by this treatment. On one of my visits to the diamond office the door opened and in walked two young men, each carrying a large enamelled saucepan containing something steaming hot. They went to one of the zinc-covered tables and turned out from the saucepans a lustrous heap of 25,000 carats of diamonds (Fig. 10). They had just been boiled in acid and washed.
After purification the diamonds are handed to the valuators (Fig. 11), who sort them into classes, according to size, colour, and purity. In the diamond office they are sorted into ten classes. In the year 1895, in 1141·8 carats of stones, the proportions of the different classes were as follows:
Close goods (best stones) 53·8 Spotted stones 75·8 Fine cleavage 79·1 Flats 39·5 Macles 36·5 Ordinary and rejection cleavage 243·4 Rejection stones 43·2 Light and brown cleavage 56·9 Rubbish 371·8 ------ 1000·0 ------ Fine sand 141·8 ------ 1141·8
It is a sight for Aladdin to see the valuators at work in the strong-room of the De Beers Company at Kimberley. The tables are literally heaped with stones won from the rough blue ground--stones of all sizes, purified, flashing, and of inestimable price; stones that will be coveted by men and women all the world over; and last, but not least, stones that are probably destined to largely influence the development and history of a whole huge continent.
Prodigious diamonds are not so uncommon as is generally supposed. Diamonds weighing over an ounce (151·5 carats) are not unfrequent at Kimberley. Some years ago, in one parcel of stones, I saw eight perfect ounce crystals, and one stone weighing 2 ounces (Fig. 12). The largest diamond from the Kimberley mines weighed 428½ carats, or nearly 4 ounces troy. It measured 1⅞ inch through the longest axis and was 1½ inch square. After cutting it weighed 228½ carats, losing 200 carats in the process. The largest known diamond was discovered in January, 1905, at the New Premier Mine, near Pretoria. This mine is of the same type as the Kimberley mines, but larger in size, and, in fact, is the largest known diamantiferous pipe in the world--the pipe containing the “blue ground,” along the longer diameter of its oval-shaped cross-section, measuring over half a mile, and its area is estimated at 350,000 square yards. This pipe breaks through felsitic rocks. The diamond, called “Cullinan” from the name of one of the directors of the company on whose farm it was discovered, was presented to King Edward on his birthday by the people of the Transvaal. It weighed no less than 3025¾ carats, or 9586·5 grains (1·37 lb. avoirdupois). It was a fragment, probably less than half, of a distorted octahedral crystal; the other portions still await discovery by some fortunate miner. The frontispiece shows this diamond in its natural size, from a photograph taken by myself. I had an opportunity of examining and experimenting with this unequalled stone before it was cut. A beam of polarised light passed in any direction through the stone, and then through an analyser, revealed colours in all cases, appearing brightest when the light passed along the greatest diameter--about 4 inches. Here the colours were very fine, but no regular figure was to be seen. Round a small black spot in the interior of the stone the colours were very vivid, changing and rotating round the spot as the analyser was turned. These observations indicated internal strain.