Young scientist's breakthrough may unlock $24 billion in invisible gold

In Witwatersrand, South Africa, there may be up to $24 billion worth of "invisible gold." A young scientist claims he knows how to extract it. The question is, is the new method cheap enough to make gold extraction profitable?

Witwatersrand is a mountain range in South Africa, about 100 kilometres long and 37 kilometres wide. At the end of the 19th century, Witwatersrand was the site of a great gold rush that contributed to the founding of Johannesburg. It is estimated that 40 percent of all the gold ever mined in the world comes from there.

The legacy of the gold rush is enormous piles of mining waste called tailings. It is these that a young scientist has become interested in.

Dr. Steve Chingwaru, a 26-year-old metallurgist from Zimbabwe, conducted research that showed that 6 billion metric tons of tailings around Johannesburg mines could contain up to 460 metric tons of so-called "invisible gold."

Gold doesn't always appear in shiny nuggets. Sometimes, microscopic amounts of this precious metal are hidden in other minerals and are not visible to the naked eye. This is what is called invisible gold.

After estimating the amount of gold hidden in the Witwatersrand waste, Chingwaru focused on more efficient methods of reprocessing these tailings - current methods are ineffective.

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 kilometers underground. Searching for gold in low-grade sources is becoming more realistic - explains Chingwaru.

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 - adds Chingwaru.

The current methods of tailings exploitation are not only ineffective but also harmful to the environment.

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 - says Chingwaru.

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 - adds the 26-year-old.

Chingwaru's research indicates that the tailings in Johannesburg contain gold worth about 450 billion rand (roughly $24 billion).

The question is whether the new method is cheap enough to make gold extraction profitable. Chingwaru claims he has spoken with several high-ranking professionals in the gold industry in South Africa, who believe the method can be scaled and become economically viable, providing substantial profits.

They all said that, yes, it would be expensive to extract the gold, they could still make a decent profit. Especially if the gold price stays where it is - said Chingwaru in an interview with Al Jazeera.