Spotlight Feature Articles - GOLD PROCESSING IM November-December 2022 - Page 2

GOLD PROCESSING

Green gold

As part of a joint venture with Heritage Minerals Pty Ltd , GreenGold Engineering is looking to reprocess historic tailings at the former operating Mount Morgan mine site in Queensland ( pictured )
The binding agreement outlines certain conditions to be met to reach a final agreement to develop the project , which includes metallurgical test work performed by GreenGold on the Windarra and Lancefield tailings to determine if its patented technology can improve gold recovery .

In the hyper aware society that governs our lives today , gold mining is continually put under the spotlight . If we are to continue to mine a metal where most of the demand is pegged to jewellery , investment and central bank buying – as opposed to metals like copper , lithium and nickel used to electrify industry and move away from fossil fuelbased power – we need to ensure that production is as energy efficient and ‘ green ’ as possible .

Many miners have received this message , aiming to reduce their carbon footprint or even achieve carbon neutrality at their operations , which , in the near term , will differentiate their products from rival gold producers .
Golden waste
One option to produce this ‘ green gold ’ is to go back to material previously labelled as waste with a new mindset and technology able to generate value .
This is exactly what GreenGold Engineering has been trying to do in recent years , tapping its ReCYN resin-based technology to recover metal complexes and make them available for sale , in the process , reducing the cyanide consumption associated with processing the material . This can also see ReCYN detoxify tailings streams and guarantee 100 % -compliant clean water discharge , according to the company .
Its technology is already being used at PT Agincourt Resources ’ Martabe gold-silver operation in Sumatra , Indonesia , to detoxify tailings and recover cyanide and copper , but , more recently , the company has been making headway in Australia .
As gold miners continue to build reserves to maintain their production profiles , they are also reducing their footprint for truly ‘ sustainable ’ operations , Dan Gleeson reports
As part of a joint venture with Heritage Minerals Pty Ltd , GreenGold is looking to reprocess historic tailings at the former operating Mount Morgan mine site in Queensland .
The two companies completed a feasibility study to determine the economic viability of this plan in 2020 , which , they said , demonstrated it is technically feasible and economically viable to treat 10 Mt of gold- and copper-bearing historic tailings over 5.5 years , with a possibility of extending the project by another 10-15 years .
ReCYN has been shown on other projects to reduce cyanide consumption by up to 50 % through capturing free cyanide from plant tailings and recycling it back into the leach circuit . Therefore , the companies believe they can deal with the higher cyanide consumption needed to treat the copper at the back end of the flowsheet at Mount Morgan , allowing them to focus on processing the gold – which represents 90 % of revenue – in a technically-simple carbon-in-leach ( CIL ) plant .
While work to refine this plan continues ,
GreenGold has been busy on the corporate activity front , signing a binding heads of agreement with Poseidon Nickel related to the processing of tailings from the Windarra Gold Tailings Project in Western Australia .
The Windarra Gold Tailings Project consists of the Windarra and Lancefield tailings with combined mineral resources of 5.96 Mt at 0.84 g / t Au and 2.1 g / t Ag , containing 180,000 oz of gold . A definitive feasibility study ( DFS ) was completed by Poseidon and released in mid- 2021 , which investigated using two different mining methods on the Windarra tailings : amphibious dredging or hydraulic mining . It also involved the construction of a modular 1.5 Mt / y processing plant to recover up to 55,000 oz of gold over a 45-month period .
“ While the outcome of the DFS was positive ,
the company is focused on the restart of the Black Swan project and decided that finding a
partner to develop and operate the Windarra Gold Tailings Project was the best outcome for shareholders ,” Poseidon said recently .
GHG-light gold
EnviroGold Global Limited ’ s circular-economy business model is designed to produce precious , critical and strategic metals while reprocessing mine waste ( tailings ), which often contains significant quantities of those valuable metals .
The company recently disclosed that the precious ( gold , silver ) and battery metals ( copper , zinc , lead ) to be produced at the company ’ s Hellyer Tailings and Buchans Tailings
reprocessing projects are expected to show a 96 % reduction in Scope 1 & 2 greenhouse gas ( GHG ) intensity per gold-ounce-equivalent produced , and an over 80 % reduction in energy intensity relative to industry averages for conventional mining . S & P Global Market Intelligence reports that typical conventional mining operations generates nearly 1 tonne of CO 2 per gold ounce produced .
In addition to recovering precious , critical and strategic metals , EnviroGold Global says it remediates the tailings consistent with environmental best practices , thereby reducing the environmental footprint of legacy mining .
EnviroGold Global recently executed a binding definitive agreement with Hellyer Gold Mines Pty Ltd ( HGM ) to reprocess the tailings owned by HGM at its namesake mine in Tasmania , Australia . The company expects to produce 965,000 oz of gold-equivalent at the operation from processing 9 Mt of total tailings feed . Test work completed to date on EnviroGold Global ’ s proprietary flowsheet demonstrated gold recovery rates of 83.5 % and silver recovery rates of 94.6 % from the refractory , volcanogenic massive sulphide tailings at Hellyer .
In 2021 , the company announced the execution of binding commercial agreements to add the Buchans River Delta Reclamation project to its portfolio . EnviroGold Global planned to
deploy proprietary modular , scalable reclamation technology and systems able to process up to 1,000 t / d of reclaimed tailings to remediate the legacy tailings while removing environmental contaminants and reclaiming valuable commodities .
EnviroGold Global CEO , Dr Mark Thorpe , said : “ EnviroGold Global ’ s Metals Without Mining business model is designed to sustainably satisfy
International Mining | NOVEMBER / DECEMBER 2022