There is an estimated R450 billion worth of ‘invisible gold’ in mine-dump tailings in the Witwatersrand, according to Steve Chingwaru, a PhD-student in geometallurgy at Stellenbosch University (SU).
The term ‘invisible gold’ refers to gold that “is hosted within a mineral, specifically sulphides, either as a very small inclusion or as a substitution within the minerals structured atomic structure”, explained Chingwaru.
Steve Chingwaru, a PhD-student in geometallurgy at Stellenbosch University defining invisible gold.
Through research, Chingwaru determined the presence of around 420 tons of gold hosted in sulphide minerals within mining dumps in the Witwatersrand region, he said. However, it is inaccessible to conventional recovery techniques, stated Chingwaru.
“[The] extraction of the gold and the host of other metals in tailings dumps could potentially deliver an economic benefit to South Africa and, importantly, contribute towards addressing an environmental legacy,” said Allan Seccombe, the head of communications at the Minerals Council of South Africa, via written correspondence with SMF News.
Economic benefits
“Gold fetches a price of over R1.2 million per kilogram, so this [research] can help to stimulate the local economy,” said Dr Bjorn von der Heyden, one of Chingwaru’s supervisors and the African Rainbow Minerals research chair in geometallurgy at SU, via written correspondence with SMF News.
“My research was to sort of determine why the gold is not being extracted at 100%. […]The stuff I’m going to do for my PhD is coming up with maybe suitable strategies for extracting this gold,” said Steve Chingwaru, a PhD-student in geometallurgy at Stellenbosch University (Pictured above). PHOTO: Hannah Theron
One of the most expensive parts of gold mining is “digging the stuff out, crushing it, and bringing it to the surface”, said Chingwaru.
This is a particular problem in the Witwatersrand as it has some of the deepest mines in the world, stated Chingwaru.
However, these mine tailings are already on the surface “just sitting there”, and so it is much cheaper to extract gold from the mine tailings, stated Chingwaru.
Steve Chingwaru, a PhD-student in geometallurgy at Stellenbosch University explaining tailings and the process of cyanidation.
Economic viability lacking
The ‘invisible gold’ from the tailings can be processed using BIOX technology, and has been attempted. This was according to Hethen Hira, head of investment relations at Pan African Resources, a gold producer focused on mining for the future. However, it is currently not economically viable to do so, added Hira.
“It would cost more to recover [the gold] than the value of [it] at this stage,” said Hira.