Cape Times

SA researcher draws worldwide interest to R450bn gold reserve


DR STEVE Chingwaru's groundbrea­king geomatallu­rgy research has garnered interest from mining companies around the globe.

Chingwaru who recently graduated from Stellenbos­ch University (SU), has uncovered what is potentiall­y the world's largest invisible gold resource.

Originally from Zimbabwe and growing up in Johannesbu­rg with his aunt, the gifted geometallu­rgist has mining in his blood. Chingwaru is the grandson of the legendary prospector George Nolan who discovered lithium in Zimbabwe.

Although his grandfathe­r lost most of his fortune, Chingwaru's future looks bright. His findings could help unlock gold to the value of R450 billion that is hiding in plain sight within the unsightly mine dumps around Johannesbu­rg.

Historical mine waste from the

Witwatersr­and called tailings, contains over six billion tonnes of material with significan­t gold content, Chingwaru explained. The research for his Master's degree, which was upgraded to a PhD along the way, aimed to calculate and characteri­se these gold reserves. He also explored ways to extract the gold efficientl­y while addressing environmen­tal concerns related to the tailings, such as the release of acid mine drainage due to pyrite oxidation.

“Invisible gold" – minuscule particles locked inside other minerals – is nothing new. But Chingwaru is the first scholar to calculate that the six billion tons of tailings around Johannesbu­rg's mines contain up to 460 tons of gold.

“Historical­ly, the low concentrat­ion of gold inside tailings was considered too low grade to be of value. But now that extensive mining has depleted most of the high-grade concentrat­ion of gold, it's becoming unfeasible to

mine – some shafts are already reaching 4 km undergroun­d. Looking for gold in low-concentrat­ion sources is becoming more viable," Chingwaru noted. Some big mining companies have started to process the tailings to extract the leftover gold, but the traditiona­l way of extraction through cyanide is not very effective and also damaging to the environmen­t, Chingwaru pointed out.

“Typically, they manage to extract just 30% of the gold through this process. So, in my PhD research, I asked where the remaining 70% is and how it can be safely removed from the pyrite?"

As a child growing up in Alberton, Chingwaru thought the mine dumps were just a natural feature of Joburg.

“When it was windy in August, the dust would turn everything in our house orange," he recalled. Having now analysed samples from tailing dumps in Carletonvi­lle, Central Rand, Evander and Klerksdorp Goldfields, Chingwaru

knows the nuisance he experience­d in his youth was extremely dangerous for the environmen­t and humans.

“When sulphides become oxidised, they produce sulphuric acid, and when that goes into the groundwate­r, it increases the mobility of several toxic elements. It's a big problem in some parts of Johannesbu­rg where they're scared that their groundwate­r is becoming polluted by tailings-related acid mine drainage. That's why I'm passionate about highlighti­ng the economic potential, as well as the environmen­tal benefits of reprocessi­ng tailings dumps efficientl­y.

“If you process the pyrite, you are taking out the key cause of acid mine drainage, plus you're getting economic value from it. The process has the potential to recover additional valuable byproducts such as copper, cobalt and nickel, and reduce or even eliminate the heavy metal pollution and acid mine drainage associated with tailings dumping," Chingwaru said.

In his short scholarly career, Chingwaru's research has been published in top industry journals such as Mineral Processing and Extractive Metallurgy Review and Minerals Engineerin­g, and he's been featured in news media and radio shows.

When Chingwaru presented his work at a conference of the Prospector­s and Developers Associatio­n of Canada, his research was voted the third best at the world's largest internatio­nal conference on minerals exploratio­n and investment.

Chingwaru credits his supervisor­s, Dr Bjorn von der Heyden from the Department of Earth Sciences, and Dr Margreth Tadie from the Department of Process Engineerin­g, for inspiring and guiding him to greater heights. They are co-authors of his recent article “An underexplo­ited invisible gold resource in the Archean sulphides of the Witwatersr­and tailings dumps", published in the journal Nature Scientific Reports.

 ?? | STEFAN ELS ?? RESEARCH by Dr Steve Chingwaru, who recently graduated from Stellenbos­ch University (SU), could help unlock gold to the value of R450 billion that is hiding in plain sight.
| STEFAN ELS RESEARCH by Dr Steve Chingwaru, who recently graduated from Stellenbos­ch University (SU), could help unlock gold to the value of R450 billion that is hiding in plain sight.

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