PhD student’s geometallurgy research uncovers massive ‘invisible gold’ resource
Obtaining a PhD at 26 is already a massive achievement, but what makes Dr Steve Chingwaru’s graduation from Stellenbosch University (SU) even more remarkable is his groundbreaking geomatallurgy research that has garnered interest from mining companies across the globe.
Chingwaru has uncovered what is potentially the world’s largest invisible gold resource, SU says in a recent media statement.
Originally from Zimbabwe and growing up in Johannesburg with his aunt, the gifted geometallurgist has mining in his blood. Chingwaru is the grandson of legendary prospector George Nolan who discovered lithium in Zimbabwe and even wrote a book, Road to Lithium Lodge, about his adventures looking for precious metals in the wilderness of what was then southern Rhodesia.
Chingwaru’s 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 tons of material with significant gold content, Chingwaru explains. 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 four kilometres underground. Looking for gold in low-concentration sources is becoming more viable,” Chingwaru says.
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 causes damage to the environment, Chingwaru points out.
In his short scholarly career, Chingwaru has become somewhat of a celebrity academic, the SU says in its media statement.
His 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 on radio shows.
At the end of last year, he was invited to a meeting hosted by the public protector in Johannesburg, to discuss the environmental impact of illegal mining.
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.