13 October 1867
13 October 1867 marks the first recorded discovery of diamonds in the colonial period of South Africa, with the very first becoming known as the Eureka diamond. By 1871, more diamonds were found in the vicinity of the present-day Kimberley, leading to the establishment of De Beers Consolidated Mines under the leadership of Cecil John Rhodes. This was soon followed by the discovery of gold, which changed South Africa's agrarian economy to an industrialized one. South Africa is to date, one of the substantial providers of minerals world-wide. Related: All that Glitters - The Discovery of Diamonds in South Africa Gold and Workers - The Mining Industry in South Africa
References

Gardner W., Discovery of Diamonds in Africa, [online], Available at: history-world.org [Accessed 8 October 2013]|Wallis, F. (2000). Nuusdagboek: Feite en Fratse oor 1000 jaar. Kaapstad: Human &Rousseau.