'Invisible' gold could be worth $24 billion in South Africa

The Witwatersrand region has tailings hills containing an estimated $24 billion worth of gold , which can be mined using new, more efficient methods.

Witwatersrand in South Africa was the site of a major gold rush in the late 19th century. Profits from gold mining were so great that it sparked the birth of the city of Johannesburg . An estimated 40% of all gold mined on Earth to date has been collected here, leaving behind huge hills of tailings (material released during the process of separating minerals from ore). Dr. Steve Chingwaru, a 26-year-old metallurgist from Zimbabwe, recently conducted research showing that 6 billion tons of tailings around mines in Johannesburg could contain up to 460 tons of "invisible gold" , IFL Science on June 28. 5 reported.

Gold mine in Witwatersrand. (Photo: 911 Metallurgist).

Gold does not always exist in bar form. Sometimes, very small amounts of gold are mixed inside other minerals and cannot be seen with the naked eye, called invisible gold . After determining the amount of gold in the Witwatersrand's tailings hills, Chingwaru's project sought a better way to reprocess the tailings to obtain gold as current methods are quite inefficient.

"Historically, low gold density inside tailings was considered worthless. But today, excessive mining has depleted most of the high-gold density ore, to the point where it can no longer be mined. Some mines have reached depths of 4 km underground. Searching for gold from low density sources is becoming more feasible. Typically, only 30% of gold can be extracted through this process , my research focuses on safely separating the remaining 70% of gold from pyrite , " Chingwaru explained.

In addition to being ineffective, current tailings mining methods also cause great harm to the environment. When sulphides oxidize, they create sulfuric acid, which mixes with groundwater, increasing the spread of some toxic elements. That's a big problem in some parts of Johannesburg, where people fear groundwater contamination from acidic water associated with tailings. The treatment process Chingwaru developed is capable of recovering valuable by-products such as copper, cobalt and nickel, while also removing heavy metal contamination and acidic water associated with tailings.

Chingwaru's research shows that tailings in Johannesburg contain gold worth up to $24 billion . The issue is whether the new method is cheap enough to mine gold and make a profit. Chingwaru said he has spoken to several people in the gold mining industry in South Africa and they think his method can be scaled up to be economically viable.