Aim-listed Goldplat’s recovery operation in South Africa, Goldplat Recovery, will be investing in a tailings retreatment project during 2018, as its growth over the past decade has resulted in the operation accumulating a large tailings stock dam.
The stock dam originates from the operation’s various carbon-in-leach (CIL) circuits. The company had always anticipated reprocessing this stock dam and, during 2016, conducted a Joint Ore Reserves Committee study to quantify the material in its tailings stock dam and determine an economic model necessary for further investment.
The content of gold and silver in its tailings stock dam is estimated to be 81 271 ounces of gold and 220 000 ounces of silver.
“Since its establishment in 1987, Goldplat has focused primarily on processing contaminated surface material and by-products produced by the primary mining operations, into which we invest most of our capital,” Goldplat FD Werner Klingenberg tells Mining Weekly.
Operating from a 22 ha freehold site based near Benoni, in Gauteng, the company has a substantial blue chip supplier base that includes all the major names of the African mining industry, such as gold miner AngloGold Ashanti, diversified miner Sibanye-Stillwater, gold miner Gold Fields, gold mining group Pan African Resources and diversified miner Impala Platinum.
Klingenberg adds that, over time, its tailings facility’s deposit has grown and, with increasing volumes and the higher gold price comes the opportunity to invest in the reprocessing of tailings.
“Goldplat Recovery’s operation is unique, compared with a standard gold mine’s metallurgical operation. “The type and grade of the material received can vary significantly, making the recovery of precious metals more challenging, whereas with a standard mine, the mineralogy of the resource is known and the metallurgical operation can forecast their recoveries more accurately.”
As a result, the grade of gold and silver contained in the tailings facility is higher than that of a standard gold mine and further recovery of those metals poses a unique metallurgical challenge.
Goldplat Recovery’s plant is designed to process various materials, such as woodchips, which are generated from underground mine supports that become caught up in the ore being processed. They are screened off after the milling stage at the mine operator’s processing plant.
The plant can also process contaminated soil and vlei-type material, which, over time, is generated around the mine and processing plant; fine carbon, which is generated when modern processing plants reprocess activated carbon for reuse in their CIL and carbon-in-pulp circuits; waste grease and mill liners, which, when replaced, are reprocessed by Goldplat Recovery to recover gold.
Any product which contains precious metals is of interest to Goldplat Recovery’s research team who will investigate methods to extract the precious metals from the different types of material available.
Goldplat Recovery’s extraction processes and multiple process lines enable it to keep materials separate, which provides a high degree of flexibility when proposing a solution for a particular type of material. The processes which are employed include roasting in a rotary kiln, fluidised bed incinerators, crushing, milling, thickening, flotation, gravity concentrators, leaching, CIL, elution and the smelting of bullion.
Testing in Progress
Goldplat Recovery has been working with the Department of Process Engineering at the Stellenbosch University, in the Western Cape, to determine through various lab-scale testwork programmes how the company can increase recoveries from its tailings reserve.
Goldplat Recovery COO Hansie van Vreden explains that all the lab-scale testwork has been concluded by the university and pilot-plant-scale testwork will be done at Goldplat Recovery’s operation in Benoni to see whether that delivers similar results, compared with the lab-scale testwork, which includes flotation and standard leaching or a combination of both.
This testwork will help determine the company’s most viable and beneficial approach to retreating its tailings stockpile and whether upgrades to its existing processing equipment would be required to achieve higher recoveries.
Van Vreden notes that the final tailings storage facility (TSF) is planned for the redundant West Pit 3 area adjacent to Goldplat Recovery’s current operation. The pit is currently a major problem for the Department of Mineral Resources (DMR) as illegal miners use the pit floor as an access point to the old underground workings.
“Over the years, the pit has become notorious for illegal mining activities and by filling the pit with tailings material, the problem of illegal mining in this specific area will be significantly reduced for the DMR.”
Goldplat is now in the process in acquiring the rights to the pit and will continue with more comprehensive environmental studies as part of the permitting and licensing requirements to determine what areas might require lining, as well as all the associated piping and pumping requirements to and from the pit.
“At our current rate of deposition, the new TSF will give us about 15 years to 20 years’ life with further options to extend the life,” Van Vreden concludes.