In the first place, there is an essential difference between the manner in which gold is found in Witwatersrand and in other districts, such as Klondyke, Senegal, or the Soudan. In the latter, the gold is in grains, either embedded between the frozen stones, or rolling in the beds of rivers. The auriferous mud is taken up and washed, and the gold is retained. Nothing could be simpler.
In the Rand, however, the working of the mines is purely scientific. The mineral is found in blocks of quartz and silicious clay containing pyrites of auriferous copper and gold.
After calculating the direction of the reef, one must dig down to a greater or less depth to find it. Dynamite is then used to detach the gold-bearing quartz, which is brought to the surface. It has the appearance of very hard white stone, slightly veined with blue. It is carried off to the batteries in Decauville trucks, and there a crushing-mill, which looks like a gigantic coffee-mill, and sledge-hammers combined into groups of five, reduce it to a very fine powder. A current of air spreads this powder over copper-plates covered with mercury.
A large proportion of the gold, about 60 per cent., amalgamates with the mercury, and once a fortnight the amalgam is scraped off. After fusion the mercury in the amalgam volatilizes, leaving a deposit of almost pure gold.
The residuum of the first process is afterwards poured into huge vats of from 10 to 12 metres in diameter, in which cyanide of potassium has been placed. A solution of cyanide of gold is thus obtained, and this is put into cases lined with strips of zinc, on which the gold is precipitated. The 40 per cent. lost in the first process is thus recovered.
The gold thus collected is melted down into ingots, the transport and verification of which are the objects of interminable regulations.
So much for the scientific part. The rest is simpler.
The heavy labour is mainly done by Kaffirs or Zulus under the supervision of white miners who earn about twenty-five pounds a month, and live in the boarding-house connected with the mine.
The natives live in a compound where no alcohol is allowed. Their rations are given them, and they live on very little. Their ambition is to earn enough money to return to their native place, buy two wives, and do no more work; the wives work for them thenceforth. It takes them about two years to realize this dream. When the time is up, it is impossible to keep them in the mines.
The first year of working (1888) yielded about £1,000,000. In 1895 about £8,000,000 was extracted. Finally, from January 1 to August 31, 1899, the harvest was nearly £13,000,000. The net profits of exploitation are considerably diminished by the enormous expenses resulting from the dearness of European labour, and the heavy taxes imposed by the Transvaal Government on mining rights and on the importation of explosives.