The Witwatersrand region has tailings containing an estimated gold value of up to $24 billion, which can potentially be extracted using more efficient new methods.
Witwatersrand in South Africa was the site of a major gold rush in the late 19th century. The profits from gold mining were so significant that they spurred the establishment of Johannesburg. It is estimated that 40% of the total gold ever mined on Earth has been extracted from this region, leaving behind massive tailings (the waste material produced during the process of separating minerals from ore). Dr. Steve Chingwaru, a 26-year-old metallurgist from Zimbabwe, recently conducted research indicating that 6 billion tons of tailings around the mining areas in Johannesburg could contain up to 460 tons of “invisible gold”, as reported by IFL Science on May 28.
Gold mine in Witwatersrand. (Photo: 911 Metallurgist).
Gold does not always exist in nugget form. Sometimes, small quantities of gold are embedded within other minerals, invisible to the naked eye, known as invisible gold. After determining the amount of gold in the waste piles of Witwatersrand, Chingwaru’s project seeks to improve the reprocessing of tailings to extract gold, as current methods are quite inefficient.
“Historically, the low gold density within tailings was considered valueless. But now, excessive mining has depleted most of the high-density ore to the point where it is no longer viable to extract. Some mines have reached depths of 4 kilometers underground. Mining gold from low-density sources is becoming more feasible. Typically, only 30% of gold can be extracted through this process. Therefore, my research focuses on safely separating the remaining 70% of gold from pyrite“, Chingwaru explained.
In addition to their inefficiency, current tailings mining methods also pose significant environmental risks. When sulfides are oxidized, they produce sulfuric acid, which contaminates groundwater and increases the spread of certain harmful elements. This is a major concern in some areas of Johannesburg, where residents fear groundwater pollution from acid water associated with tailings. The processing method developed by Chingwaru has the potential to recover valuable by-products such as copper, cobalt, and nickel while removing heavy metal pollution and acid water linked to tailings.
Chingwaru’s research indicates that the tailings in Johannesburg contain gold worth up to $24 billion. The question remains whether the new method is cost-effective enough to extract the gold and generate profit. Chingwaru mentioned that he has spoken with several people in the South African mining industry, and they believe his method could be scaled up to be economically viable.
