The concentrates recovered by the frue vanners are generally treated by chlorination (roasted). This process is gone through so that the iron can be separated from the gold. Concentrates are sometimes treated by cyanide, but the process, if cheaper, is slow and less effective. Chlorinated gold is also smelted into bars.
Cyanide.—The gold from the zinc shavings is recovered by retorting. It is afterwards melted into bars and called 'cyanide gold.'
Slimes (or float gold) are generally conserved in a dam, and when the quantity is sufficient they are treated by chlorination, or by a solution of cyanide of potassium.
After treatment all sand is still retained, and is really a small unbooked asset of the various gold-mining companies. The Rand undoubtedly is the best field to-day for students who wish to acquire the details of gold recovery. In no other country has science produced such excellent results. At least 95 per cent. of the gold in the ore can now be recovered, and scientific men from all countries are resident on the fields, and advantageous discoveries in the treatment of various ores are of almost daily occurrence.
STORY OF THE SOUTH AFRICAN GOLD-FIELDS.
There is material for the philosopher in the fact of gold-finding having occurred in connection with a part of the world to which King Solomon the Wise sent for supplies of gold and 'almug-trees,' for the mysterious Ophir has been located in Mashonaland, and the Queen of Sheba identified with the Sabia districts, which, though not in 'the Randt,' are curiously connected with the rise and progress of the mania.
Let us briefly trace that romantic history, merely mentioning by the way that, even in European history, African gold is no novelty, for the Portuguese brought back gold-dust (and negro slaves) from Cape Bojador four hundred and fifty years ago. The ruins of Mashonaland were discovered in 1864 by Karl Mauch, who also discovered the gold-field of Taté on the Zambesi, of which Livingstone had reported that the natives got gold there by washing, being too lazy to dig for it. When Karl Mauch came back to civilisation, people laughed at his stories of ruined cities in the centre of Africa as travellers' fables, but a number of Australian gold-diggers thought his report of the Taté gold-field good enough to follow up. So about 1867, a band of them went out and set up a small battery on the Taté River for crushing the quartz. This may be called the first serious attempt at gold-mining in South Africa since the days of the lost races who built the cities whose ruins Karl Mauch discovered and which Mr Theodore Bent has described. A Natal company assisted the Taté diggers with supplies, and enough gold was found to justify the floating of the Limpopo Mining Company in London. This was in 1868, and was practically the foundation of the 'Kaffir Circus,' though its founders knew it not. Sir John Swinburne was the moving spirit of this enterprise, and went out with a lot of expensive machinery, only to meet with a good deal of disappointment. The diamond discoveries in Griqualand soon drew away the gold-seekers, who found the working expenses too heavy to leave gold-mining profitable, and for a time the Taté fields were deserted. They were taken up again, however, twenty years later by a Kimberley enterprise, out of which developed the Taté Concession and Exploration Company, to whom the unfortunate potentate Lobengula granted a mining concession over no less than eight hundred thousand square miles of Matabeleland.
Just as the Australians were breaking ground on the Taté, Thomas Baines, the traveller, was making up his mind to test the truth of tales of gold in the far interior, which the Portuguese from Da Gama onwards had received from natives. In 1869 he set forth from Natal with a small expedition, and in 1870 received from Lobengula permission to dig for gold anywhere between the rivers Gwailo and Ganyona. Some seventeen years later this same concession was repeated to Mr Rudd, and became the basis from which sprang the great Chartered Company of British South Africa.
In the course of his journey, Baines encamped on the site of the present city of Johannesburg, without having the least idea of the wealth beneath him, and intent only upon that he hoped to find farther inland. On the map which he prepared of this journey is marked the 'farm of H. Hartley, pioneer of the gold-fields,' in the Witwatersrandt district. Hartley was known to the Boers as 'Oude Baas,' and was a famous elephant-hunter, but as ignorant as Baines himself that he was dwelling on the top of a gold-reef. And it was not in the Witwatersrandt, foremost as it now is, that the African gold boom began.