In the grand scheme of things, a ninetieth anniversary of a mineral discovery should not be worth much fanfare. However, given that South Africa’s commercial mining sector is relatively young, dating back only 162 years, and taking into account the negative light in which the industry has been cast recently, particularly during the five-month-long Platinum Belt strike, such a commemoration should not be taken for granted.

It was during the month of September, exactly 90 years ago, that Dr Hans Merensky made one of South Africa’s most important and economy-driving mineral discoveries when he uncovered the platiniferous reef in the eastern limb of the Bushveld Igneous Complex (BIC), near the town of Mashishing (Lydenburg), in Mpumulanga. (While Merensky should certainly be credited with the discovery of the main platinum-bearing orebody, it should be mentioned, for the sake of historical accuracy, that the occurrence of two platinum-group metals (PGMs) – osmium and iridium – was identified in concentrates from the Witwatersrand’s gold ores as early as 1892. Moreover, the occurrence of platinum in the Rustenburg district was first reported in 1908 by two geologists undertaking investigations for the South African Geological Survey, but the mineralisation was believed to be insignificant and the discovery was not deemed worthy of further investigation.)

The story of the discovery of the BIC begins not with Merensky himself but with a certain Andries Lombaard, an Eastern Transvaal farmer and amateur prospector who panned for gold in the streams of his farm, Maandagshoek, some 60 km north of Lydenburg. It was while panning for gold in the autumn of 1924 that Lombaard came across small silvery grains in the concentrate in his pan. Not being entirely certain what the metal was, although having a suspicion it could be platinum, Lombaard sent a sample of the alluvial gravel for analysis to Merensky, who, at the time, was the most renowned and trusted geologist among the Transvaal farming community.

Merensky tested the gravel at a specialist laboratory in Johannesburg and identified the silvery grey metal as platinum and also picked up traces of rhodium and iridium. Encouraged by such a result, Lombaard invited Merensky to undertake geological investigations in the vicinity of the discovery. Merensky’s curiosity had been piqued and, so, in July of that year, he arrived at Mandaagshoek to begin prospecting with the assistance of Lombaard and his two cousins.

Merensky wrote: “On arrival at the farm, I inspected the geological features. I observed that the alluvial in some spruits carried values, whereas in other spruits in almost the immediate vicinity only blanks resulted. I noticed, too, that the rocks in the neighbourhood showed great magmatic differentiation. These two facts together gave me cause for optimism. I argued that these rocks might carry payable values dissimilar to the experience in the Urals and Colombia.”

Merensky was so encouraged by these results that he decided to leave all other work for a few months to follow up the new find. However, an intensive exploration programme of the wider vicinity required financial support and Merensky was required to return to Johannesburg to raise the necessary funds.

He approached his circle of German friends to provide financial backing for the venture and was able to raise £2 000 and, in the process, form the LP Syndicate – ‘LP’ secretly standing for Lydenburg Platinum – to investigate and exploit any payable platinum deposits that might be discovered. Under a veil of secrecy, as Merensky wanted to prospect as much of the area as possible before other prospectors and mining companies got wind of the discovery, the syndicate secured mineral right options over the farms Mandaagshoek, Hendriksplaats (adjoining Onverwacht) and Leeuwvallei.

In mid-August, Merensky and his team began to intensively prospect the Lydenburg district, using Maandagshoek as a base. In just three days, the party succeeded in determining the existence of platinum in the ultrabasic rocks of the neighbouring Mooihoek farm. Encouraged by these results, Merensky reported the discovery to the local mining commissioner, based at Pilgrim’s Rest, and secured 23 claims on that farm. Because news of the discovery was expected to spread like wildfire and attract the attention of many other prospectors, the party was in a race against time to secure as much of the prospective area and, as a result, worked quickly to locate other platinum occurrences in the vicinity.

Fortunately, Merensky managed to keep ahead of the prospectors who had become aware of his discoveries. In early September, he successfully located the platinum-bearing stratification that would subsequently be christened the Merensky reef to honour his great geological achievement. The most noteworthy aspect of this find was that the rock, which was darker in colour and contained all kinds of sulphide minerals, displayed a type of igneous layering that could be followed for some distance. The team worked extensively along the ranges and hills of the Lydenburg district and, after a number of weeks, ascertained that the platiniferous belt ran, from its northernmost to its southernmost spur, for some 160 km.

Interestingly, it would only be the following year, in early 1925, when the attention of South Africa’s prospecting and mining community was firmly focused on the Eastern Tranvaal, that Merensky would discover the western limb of the world-famous BIC.