The Witwatersrand Basin is the richest gold field the world has ever known, yielding over 1.5 billion gold ounces since mining began in the late 19th century which amounts to third of all the gold that has ever been produced.
The Basin was discovered in 1886 by an Australian prospector called George Harrison.
While some gold had been discovered previously in what was then the eastern Transvaal (today’s Mpumalanga Province), it was South Africa’s diamonds that were attracting international attention at that time, having been discovered twenty years previously in an area to the south west of the Witwatersrand Basin which would later become the town of Kimberley. The region was heaving with diggers and investors and a small group of diamond entrepreneurs had established themselves, Cecil John Rhodes among them, and started to consolidate commercial control, amassing immense diamond fortunes for themselves and their companies.
Gold had been more elusive up to that point and Harrison’s discovery came after several years of painstaking, and to date futile, prospecting work had been done in the area. The unusual geology of the Witwatersrand Basin, which forms a stratigraphic series of thin gold-bearing bands or reefs which outcrop briefly along the edges of the Basin and then dip down steeply towards the centre, apparently disappearing under later geological layers, created additional challenges for the early prospectors.
However, once news of Harrison’s discovery began to spread and the outcrops of the gold-bearing reefs could be traced, prospectors flocked to the area, at first from the diamond fields and smaller eastern Transvaal goldfields but soon, from all over the world. Johannesburg, the city of gold, was born.
Initially, it seemed that the boom would be short-lived, as it became clear that the shallow gold would run out fairly quickly, leaving room only for the already wealthy few who could afford to go deeper. More importantly, it was difficult to extract a profitable amount of gold from the Witwatersrand host-ore, as it occurred in very fine flecks sprinkled throughout the rock, rather than in the larger granules or loose alluvial sand which was what the world had so far been used to.
But in 1887, a significant new technology was fortuitously discovered in Scotland, namely the extraction of gold using cyanide, a process which raised the level of gold recovery from approximately 65% to 95%.
This reinvigorated the Johannesburg gold rush, and as the activity continued to grow so more reefs and goldfields were discovered and improved technology enabled deeper and deeper mining.
This boom has continued for over a century and while many of the Witwatersrand Basin’s mines have now been exhausted, it remains one of the world’s premier gold mining locations, with many of the world’s biggest mining companies still very active in its goldfields.