Waste not, want not: Finding ore in mining waste
by Ina King (Potgieter) June 13, 2019
Although the mining industry has played a vital role in economic development, it remains one of the biggest contributors to pollution worldwide. As South Africa dips further into financial strife, combining smart spend with environmental management and metal recovery is becoming standard procedure.
Introduction
The mining sector has been struggling in a tough economic climate for years. Rather than following the traditional path from prospecting to closure as finite resources are depleted, treating waste as a potential resource could help the industry. Mine site rehabilitation can be expensive, but thanks to new technologies and new mind-sets, mine tailings can be re-mined. In our current economic climate, it makes financial sense to utilise already extracted ore and re-mine rather than looking for new sites to mine.
The modern need for raw materials
According to a Mintek database, there are more than 446 gold tailings dumps spanning more than 18 000 ha across Johannesburg. All mines create waste dumps which contain the entire mine’s waste, left unprocessed.
Raw materials are essential for modern societies. From medicine to cars, computers to cosmetics and everything in between, of the ninety two elements in the earth, forty of them are used in our daily lives. The world is indeed changing and many metals, metalloids or rare earth elements which had no application in the past are now used for the manufacture of high added value products especially in new and green technologies.
The good news is that with new technologies allowing for the re-mining of unprocessed ore so there’s no need for a new mine and minerals like lithium and uranium can be recovered from much lower-grade materials.
Breathing new life into mining waste
Older mining techniques had lower recovery rates than today’s technology. So, the older the mine, the greater the proportion of the target mineral that is likely to be left over. Industry leaders believe that significant volumes have been left behind in mines like those in Barberton, Mpumalanga.
Despite often being labelled as a key mining legacy and considered one of “the old miners’ mistakes”, tailings offer a new capitalisation route. The retreatment of tailings for gold, uranium and sulphides is invaluable in an industry beset with financial constraints.
With various techniques and technologies, including flotation, and given the amounts of tailings scattered across the ‘Golden Arc’ (from Johannesburg to Welkom), there is potential for the creation of a vibrant tailings retreatment industry in South Africa.
DRDGold believes that re-mining tailings is also an effective way for the industry to address the “scar tissue” associated with the mine dumps and to positively impact the economy socio-economic development. Tailings retreatment, unlike traditional underground mining techniques, is less labour-intensive, has increased levels of safety, and is socially and environmentally responsible.
Conclusion
Traditional mining is expensive and re-mining materials that have already been extracted from the ground is certainly a cheaper option.
Increasingly lower ore grades, deeper underground mining, high labour costs, and soaring electricity highlight the need for cheaper mining options. “These factors are also accelerating gold tailings retreatment operations in South Africa”, according to Sibanye’s West Rand Tailings Retreatment Project (WRTRP).
The objective in Johannesburg is to recover uranium and residual gold from abandoned mine tailings and to oxidise the sulphides to eliminate long-term environmental liability. Reclaiming and re-mining ore from tailings, is a win-win situation all round.
