Tag Archives: heap leaching

McEwen Mining progresses gold-silver heap leach plan at Fenix

McEwen Mining looks to have found a way to prolong its operations at the El Gallo Complex in Sinaloa, Mexico, with the feasibility study for its 100%-owned Fenix project highlighting a 9.5-year operational blueprint.

Using gold and silver prices of $1,500/oz and $17/oz, McEwen has estimated an operation able to produce 26,000 oz of gold production in phase one (years one to six) and 4.2 Moz of silver-equivalent in phase two (years seven to nine-and-a-half).

Phase one comes with an initial capital bill of $42 million and an all-in sustaining cost (AISC) estimate of $1,042/oz of gold. Phase two would require a $24 million incremental capital injection in year six, with the AISC calculated at $14.28/oz of silver-equivalent.

The company’s El Gallo mine (pictured) produced 240,000 oz of gold and 125,000 oz of silver from 2012-2017, yet, due to the transition to deeper sulphide mineralisation not amenable to heap leaching, mining and crushing activities ceased in the June quarter of 2018.

While residual heap leaching is set to continue to produce gold for several years, the company has been working on a new project for the El Gallo Complex, which is where Fenix comes in.

The Fenix 2018 preliminary economic assessment evaluated the potential extension of production in the complex, based on a two-phased transformation of the processing from the El Gallo mine, innovative in-pit tailings disposal and sourcing from several deposits.

The latest feasibility study has run with that plan, with the critical path environmental permits in hand for the first phase of production, according to Rob McEwen, Chairman and Chief Owner of McEwen Mining.

“Our next steps will involve detailed engineering, assessment of procurement options and the evaluation of financing alternatives,” Rob McEwen said.

He added: “The project will incorporate an environmentally progressive method of tailings management, using in-pit storage that creates multiple benefits, most importantly a secure containment of tailings, enabling better reclamation results.”

Corvus Gold weighs heap leach, BIOX route at Mother Lode project

Corvus Gold has announced the results of a preliminary economic assessment (PEA) for its Mother Lode project (MLP) in southwest Nevada, USA.

The study outlines a project able to produce 170,980 oz/y of gold and 79,600 oz/y of silver through a combination of heap leaching and biological oxidation (BIOX).

Based off measured and indicated resources of 1.55 Moz of gold and 1.51 Moz of silver, and inferred resources of 170,000 oz of gold and 400,000 oz of silver, the study estimated an operation with an eight-year mine life and an initial price tag of $406 million. Using a $1,500/oz gold price, the payback period was estimated at 2.7 years.

Jeffrey Pontius, President and CEO of Corvus, said: “The results from our initial PEA study of the Mother Lode standalone project are encouraging. The potential projected annual gold production of over 200,000 oz/y during the first three years is significant, especially as a new project, which could provide an increase to the Corvus Gold future production profile. The PEA demonstrates the preliminary potential for the project, on its own, to produce significant free cash flow and after-tax NPV.

“Corvus now has a number of strategic alternatives available to it to drive shareholder value. Given the recent interest in the Bullfrog Gold District from multiple producing companies with adjacent land packages, Corvus’ compelling and accretive projects and its commanding land position with what we believe is demonstrated high exploration potential, has positioned the company to deliver increased shareholder value.”

The Mother Lode project is modelled as a large, open pit, with a biological oxidation mill to treat the higher-grade sulphide mineralisation and a heap leach pad for treatment of oxide mineralisation. The mining plan uses standard mining practices and has a production scale that is currently being used by many operating mines, the company said.

The new PEA study, which assumes a standalone project, also includes a number of other changes to the previously assumed concept for the combined Mother Lode-North Bullfrog project configuration, which enhance the project. This includes:

  • Employing BIOX to treat the MLP sulphide mineralisation would increase gold recovery by 11%. Metallurgical testing of a stirred BIOX process on the MLP whole sulphide mineralisation from Mother Lode demonstrated gold recoveries of 91-92% as compared with the previous testing on MLP flotation concentrate;
  • Eliminating the need for the concentrator, oxygen plant and autoclave components of the previous plant concept simplified the plant conceptual design and would reduce the process plant capital cost;
  • Ongoing work expanding Mother Lode resources in the CIZ area and the main Zone with ongoing work at improving the open-pit mining and development plans will enhance project economics; and
  • New experimental work on conducting the BIOX process in a heap is being tested as follow-up on past successful studies and could substantially cut operation and capital costs with the elimination of the mill circuit.

The PEA only includes drill results completed up until September 2020. In addition, Corvus will continue follow-up mineral resource expansion work and new discovery drilling on priority targets at both the North Bullfrog and Mother Lode properties through 2021, it said.

Rio2 to test Sixth Wave’s IXOS polymer tech at Fenix heap leach gold project

Sixth Wave Innovations Inc and Rio2 Ltd have executed a non-binding Letter of Intent for the trialling of Sixth Wave’s patented IXOS® purification polymer at the Fenix gold project in Chile.

Under the terms of the LOI, Rio2 will send representative ore samples from its Fenix project to Sixth Wave for testing and analysis in its Salt Lake City, Utah, facility. Sixth Wave will perform a combination of leaching and recovery tests using its IXOS technology on these samples consistent with protocols for the expected heap leach mining activity planned for Fenix.

Upon completion of the testing, to be performed in October, and pending positive results, the two companies will work to negotiate a definitive agreement to proceed to a complete on-site pilot adsorption/desorption/recovery (ADR) plant scaled to operate on a 400 t pilot leach pad.

A prefeasibility study on Fenix outlined a heap leach gold mine producing an average of 93,000 oz/y during the first 13 years and 50,000 oz/y during the final three years of production as stockpiled ore is being crushed and leached.

IXOS, meanwhile, has been demonstrated to capture up to 99% of gold from cyanide leach solutions in laboratory and mine site testing where the data was analysed by the mine operator, representing a material increase relative to activated carbon, which recovers between 85% and 95% of the gold, as reported by potential mining customers of IXOS. Additionally, the increased selectivity of IXOS results in the capture of fewer other competitive base metals, Sixth Wave says.

Testing at multiple mine sites has shown more than 90% gold purity captured on IXOS, as opposed to 40%-70% for those generated by activated carbon, resulting in efficiencies in the refining process used to generate higher purities of gold.

The objective of this work, from Rio2’s perspective, is to determine whether Sixth Wave’s IXOS technology can be successfully applied to enhance the extraction of gold from Fenix gold ore by using molecularly imprinted polymers rather than traditional carbon for the gold adsorption process.

If successful, the application of IXOS is expected to result in a reduction of capital expenditure and operating expenditure related to the gold extraction process.

Upon successful completion and positive results of the pilot program, the companies would then move to an implementation phase incorporating IXOS into the actual processing plant to be constructed at Fenix.

Dr Jon Gluckman, President and CEO of Sixth Wave Innovations Inc, said: “We are very excited about this project and working with Rio2. The IXOS process should excel in comparison to traditional activated carbon because of the high rejection of base metal and scaling and the smaller process plant required for IXOS. Substantially lower power consumption in the desorption and recovery stages, and no need for regeneration, will also play a large role in reduced opex.”

He added: “It is exciting to be involved with Rio2 at this phase of the Fenix gold project as it allows us the ability to optimise the design of the ADR circuit without having to worry about retrofit constraints.”

Alex Black, President and CEO of Rio2, said: “Rio2 is always looking to embrace and trial new technology with the objective of bringing enhanced value to our stakeholders through the reduced capex/opex opportunities that innovative technologies can bring.

“The Fenix gold project is currently the largest undeveloped gold heap leach project in the Americas and we look forward to working alongside Sixth Wave during the development phase of the project.”

Hycroft Mining ups the proprietary heap leach process ante

Hycroft Mining Holding Corp has continued to demonstrate the viability of its proprietary heap leach oxidation process at its Hycroft gold mine in Nevada, USA, over the June quarter, with the company hitting several milestones.

The Hycroft gold-silver mine was restarted in 2019 to demonstrate this process, which oxidises sulphides prior to leaching, on a commercial scale. Based on the success of initial operations and a 2019 feasibility study, Hycroft began implementing the long-term mine plan with the start of construction in April 2020 of the first phase of a large leach pad capable of processing the resource base with more than 30 years of mine life.

While gold and silver production fell below expectations over the period, the company was able to demonstrate the process on initial leach pads one and two at Hycroft, achieving higher than feasibility level gold recoveries for Brimstone ore (82% versus 65% in the feasibility study) and Central ore (91% versus 70% in the feasibility study).

It also improved the solution management system to increase solution distribution to the leach pads, while commencing the leach pad expansion on the north side of the mine in anticipation of starting heap leach stacking in the December quarter of 2020, Hycroft said.

The expansion project will provide the company with the leach pad space required for future operations, the company added.

“The initial stage of the leach pad project is being constructed in two phases by a contractor, with the first phase consisting of approximately 4 million sq.ft (3.7 million sq.m) of pad space and infrastructure for ponds, pipes and electricity, and the second phase consisting of approximately 4.6 million sq.ft, which we expect to construct in 2021,” the company said.

“With respect to the first phase, we expect the earthworks and leach pad construction to be completed in the fourth (December) quarter of 2020 and infrastructure completed and initially commissioned shortly thereafter.”

On the process side, the downstream process infrastructure is in place to ramp up operations. Hycroft is currently operating the Brimstone Merrill-Crowe facility and refinery, but it has begun planning to restart the 21,500 gallons/min (1,629 l/s) North Merrill-Crowe plant in 2021 to meet increasing solution flows from the new leach pad.

To facilitate these heap leach changes, the company expanded its mining fleet with the rental of seven 240 ton (218 t) trucks and one loader to increase mining capabilities over the quarter. It also improved its mobile equipment maintenance team to transition to self-performed maintenance and discontinue the contractor-led maintenance applied since start-up. Lastly, it began active in-pit drilling and blasting of fresh ore and reduced the mining of stockpiles.

On the crusher side, it refurbished and recommissioned the crushing system, which saw the average amount of material crushed go from 338,000 tons/mth (306,628 t/mth) in the March quarter to 459,000 tons/mth in the June quarter, an increase of 36%. It also established a comprehensive preventative maintenance program and initiated an ongoing operator training program to improve crusher efficiency and reduce downtime.

Steve Jones, Interim President and CEO of Hycroft Mining, said: “There have been a number of improvements at the mine recently that are building a strong foundation for the next phase of operations, including adding experienced technical people and increasing the reliability of process infrastructure.

“While the next few months are still considered to be transitional, we are looking forward to utilisation of the new leach pad and being able to ramp up to feasibility study operating levels.”

Centerra Gold’s Öksüt mine comes to life with first pour

Centerra Gold has achieved the first gold pour from its Öksüt mine, in Turkey, on schedule and ahead of budget.

Additionally, the project achieved a significant safety milestone last week, achieving two million work hours lost time injury free.

Scott Perry, President and Chief Executive Officer of Centerra, said: “This is an important milestone for the project and for the growth of the company as Öksüt is now our third operating mine and our third source of gold production going forward. Reaching the first gold pour is a testament to the dedication and hard work that our Öksüt team has put in to reach this goal safely.”

He added: “This milestone would not have been achieved without the initial conviction and perseverance from the Centerra exploration team given that the Öksüt mine, originally started as a greenfield exploration venture in 2009.”

Öksüt was planned as a conventional truck and shovel open-pit heap leach mining operation with a stacking rate of 11,000 t/d. The initial eight-year mine life was expected to process around 1.2 million contained ounces of gold from two open pits, the Keltepe pit and the smaller Güneytepe pit.

BHP’s Jurgens presents big picture automation plan

Diane Jurgens, BHP’s Chief Technology Officer, used her time on stage at the Bank of America Merrill Lynch SmartMine conference, in London, to highlight the company’s plan to introduce full or partial automation across its entire value chain.

The miner has already introduced automation across many of its operations – from haul trucks at Jimblebar (Western Australia) to drill rigs at Western Australia Iron Ore – but Jurgens said the company has bigger automated plans.

This includes considering opportunities to accelerate truck autonomy across the company’s Australia and Minerals Americas sites – the company previously detailed plans to automate around 500 haul trucks across its Western Australia Iron Ore and Queensland Coal sites – and introducing “Decision Automation” to link autonomous processes and data from different sources together to create “near instantaneous, optimised decision making”, Jurgens said.

While she talked up the use of automation in mining – referencing the experience she has in the automotive and aerospace industries – she admitted full automation across the BHP group was unlikely.

“This is because we automate equipment and processes where it provides the highest value,” she said, explaining that investment in technology competes against all of other projects in the BHP portfolio, “and alternative uses of cash, under BHP’s Capital Allocation Framework”.

To test this, the company has built proving grounds at two active mine sites (Eastern Ridge in Australia and Escondida in Chile) to trial new innovations in geology, extraction and processes, and “develop workforce capability so that our people are equipped for the rapid pace of change that lies ahead”, Jurgens said.

Just some of the new innovations Jurgens mentioned included the use of advanced geophysics modelling to reanalyse existing drilling data. This new approach led, in November last year, to the Oak Dam copper discovery, near its existing Olympic Dam operations in South Australia.

Recently, sensors were installed at the Escondida test grounds to prototype the use of real-time data to analyse the quality and grade of ores and inform, for example, whether to divert unprocessed ore for leaching, to concentrators or waste. Jurgens said: “The key to achieving this is using data collected through the sensors and combining it with proprietary algorithms. We then apply our knowledge of the ore body to optimise the processing methods. Once in production, we expect these to improve throughput performance.”

With access to more detailed data on extracted material, machine algorithms can automate decisions to identify and divert waste, which increases plant performance and reduces processing costs, she added.

New patented leaching technologies have, meanwhile, increased metal recoveries by 10-12% and shortened the processing time by 50%, according to Jurgens. “At Spence in Chile we increased copper recoveries by about 10% and helped offset grade decline through implementing the low-cost Spence Recovery Optimisation project,” she said. “The initiative improved heap leach kinetics which meant we could maximise utilisation of the leach pads and therefore use the full 200,000 t of tankhouse capacity.”

This breakthrough also informed the successful heap leach trial at Olympic Dam, which the company has just completed.

The company’s automation and innovation journey has already resulted in significant wins, according to Jurgens.
Equipment automation is creating more efficient, standardised and safer operations, she said:

  • Autonomous blast hole drills across BHP’s Western Australia Iron Ore assets have increased drill rates by 25%, and reduced monthly drill maintenance costs by over 40%;
  • Haulage automation at the Jimblebar operation, in the Pilbara, has reduced heavy vehicle safety incidents by 80%;
  • Machine learning is being applied to maintenance on trucks in iron ore and coal – to analyse component failure history;
  • At Yandi, haul truck maintenance analytics increased truck availability to above 90% and generated recurrent cost savings. Replicating these strategies to our trucks in energy coal in the Hunter Valley, BHP has also seen an increase in truck availability;
  • Automating key components of BHP’s rail network is supporting increased capacity, more reliable dispatch and improved maintenance outcomes;
  • In Western Australia, material density scanning and laser precision have delivered an additional 2.4 t of iron ore per car while reducing safety risks of overloading;
  • The automated rail network scheduling system, which controls over 10,000 ore cars and transports about 270 Mt/y of iron ore, is becoming more effective through self-learning algorithms, ensuring trains arrive at port, on-time, and;
  • LiDAR technologies are being used to automate the loading of ships that transport BHP’s product to customers around the world.

BHP and Bureau Veritas confirm heap leach viability for Olympic Dam

BHP says it has successfully completed its heap leach research and development trial in South Australia, confirming the viability of the technology to extract copper, uranium, gold and silver at Olympic Dam.

The program began in 2012 and was conducted at a purpose-built, small-scale heap leach facility at Wingfield run by Bureau Veritas, under direction from BHP and with support from the South Australia Government.

BHP’s General Manager of Olympic Dam’s Surface Processing, Chris Barnesby, made the announcement at the Copper to the World conference in Adelaide on June 18.

“The promising results from this trial supports our positive outlook for Olympic Dam, given forecast demand increases for copper and the optionality we are building for this world-scale resource,” he said.

“We safely and successfully produced 19 t of good quality copper, most of which went back into the smelter and off to customers, though we kept a little to ourselves to commemorate the achievement.”

Despite the success of the project, Barnesby said the deployment of such technology was a “matter for future consideration”, explaining that there were many factors involved in making this decision, including “passing through our Capital Allocation Framework”.

He concluded: “As it stands today, we have confirmed the viability of a technology with the potential to join our suite of growth options. However, our immediate focus is on operating safely and reliably, and setting a foundation to unlock more value for BHP and for South Australia over the long term.”

Heap leaching works by drip-feeding acid through a large stockpile (or heap) of ore to leach out metals. BHP uses heap leaching at its copper operations in Chile, however Olympic Dam’s polymetallic properties require a different approach, according to the miner.

BHP said: “The research and development program has the potential to benefit the mining industry more broadly in South Australia, as heap leaching has the potential to deliver lower capital and operating costs, increased scalability, reduced potable water use and the ability to process lower-grade ores.”

Separate to the trial, BHP continues to progress studies on the Brownfield Expansion project, or BFX, as part of Olympic Dam’s resource development strategy, which seeks to potentially increase production to between 240,000-3000,000 t/y of copper.

Eldorado Gold to continue heap leaching operations at Kisladag

Eldorado Gold has decided to resume mining, crushing, stacking and heap leaching at its Kisladag gold mine, in Turkey, and suspended plans to build a $500 million processing plant.

The decision comes following the receipt of metallurgical test work on material placed on the heap leach pad last year.

Not only will this move defer a significant amount of capital expenditure for the company, it is also expected to help production rise to 390,000-420,000 oz in 2019, compared with 349,147 oz in 2018, a year when Eldorado suspended mining operations at Kisladag due to lower than expected gold recoveries.

Eldorado’s President and CEO, George Burns, said: “The decision to restart mining and heap leaching at Kisladag is supported by improved heap leach recoveries and confirmed by a revised heap leaching plan developed in early 2019. The revised heap leaching plan results in favourable economics when compared to milling, without the risks associated with the construction and financing of a $500 million project.”

On October 23, 2017, the company provided an update on Kisladag operations based on laboratory testwork undertaken during the September quarter of that year, which indicated that lower recoveries were expected from the zone of mineralisation located around the base of the open pit where mining was underway.

Based on available information, in the March quarter 2018, Eldorado elected to suspend mining in order to evaluate processing options. Following a year of engineering and testwork, in October 2018 the company announced that the Board of Directors had approved the advancement of a mill project. Subsequent to that announcement, gold recovery from the leach pad increasingly exceeded expectations. The company then focused testwork and analysis on the viability of resuming mining and heap leaching at Kisladag.

In parallel to mill engineering and analysis, testwork to extract maximum value from material already placed on the heap leach pad and the remaining reserves was ongoing throughout 2018.

Approximately 900,000 t of ore was placed on an inter-lift lined test pad in the March quarter of 2018. Late in the year, results from this pad were showing recoveries of approximately 58% from an extended leach cycle approaching 250 days (compared with around 40% recoveries from the original 90-day column tests).

In early 2019, the company analysed the new data and developed revised heap leaching plans, showing improved economics for the heap leaching scenario, hence the recent decision.

Eldorado said mining was expected to recommence by the end of this quarter, with the three-year guidance of 145,000-165,000 oz (2019), 240,000-260,000 oz (2020) and 75,000-95,000 oz (2021) based on mining and stacking an initial 22 Mt of ore grading over 1.1 g/t over this period, as well as continuing to leach the material currently on the pad.

This would help overall group production go to 390,000-420,000 oz in 2019, 520,000-550,000 oz in 2020 and 350,000-380,000 oz in 2021.

Eldorado said on Kisladag: “While the mill project has been suspended, the project remains viable in the short-term. The viability of the mill project will continue to be assessed in light of the results from ongoing heap leach metallurgical testwork on deeper material and in view of other investment opportunities within the portfolio,” the company said.

The other piece of exciting news within the company’s results was developments at its Lamaque mine in Quebec, Canada.

The company poured first gold from the Sigma mill at Lamaque in December and, in the March quarter, the mine is expected to declare commercial production. This should set the operation up to produce 100,000-110,000 oz of gold in 2019 from the mining and processing of over 500,000 t of ore at an average grade of 7 g/t Au.

Burns said: “At Lamaque, we are very pleased with the performance of our project team who delivered the first gold pour from the Sigma mill in less than 18 months since acquisition.”

In addition, exploration success at Lamaque – which includes significant resource conversion in the C5 orebody, in particular – has led the company to review options to increase throughput at the Sigma mill.

Eldorado said: “The mill has a refurbished nameplate capacity of 2,200 t/d and the potential to expand to its former capacity of 5,000 t/d with a purchase and installation of a SAG mill. Based on planned drilling and the potential conversion of inferred resources in C4, C5 and C6, the company expects to explore options to increase mill feed.”

The Lamaque underground mine is currently expected to produce 125,000-135,000 oz of gold in both 2020 and 2021.

Leagold planning Los Filos gold mine expansion following latest study

A feasibility study on the expansion of Leagold Mining’s Los Filos mine, in Mexico, has shown potential for the development of the Bermejal underground mine, enlarging the Los Filos open pit, re-phasing the Bermejal open pit into two distinct open pits (Bermejal and Guadalupe), and construction of a carbon-in-leach (CIL) processing facility.

The study shows total gold production of 3.3 Moz over a 10-year mine life (2019 to 2028) at an average all-in sustaining cost of $795/oz at Los Filos. Post expansion (2021 onwards), average annual production would step up to 350,000 oz at an AISC of $759/oz, compared with 195,362 oz last year, which came from the existing heap leach facilities.

The capital cost came out at $180 million to develop the Bermejal underground and construct a new 4,000 t/d CIL plant with related infrastructure, with an NPV (5% discount) of $565 million generated using an average gold price of $1,250/oz.

Leagold CEO, Neil Woodyer, said: “When we acquired Los Filos in April 2017 from Goldcorp, we identified its potential to be developed into a long-life, low-cost operation with significant scale. During the 20 months since the acquisition, we have carried out extensive exploration programmes for both open pit and underground deposits, developed a 1,330-m ramp to access the orebody at Bermejal underground, completed the Bermejal underground mine design, completed comprehensive metallurgical testwork on all of the mineral deposits to support the CIL plant design, and learned a lot from current operations.

“The study identifies a new operating strategy, which includes three large open pits, two high-grade underground mines, the addition of a CIL plant to process the higher-grade ore, and the continued heap leaching of the lower-grade open-pit ore. The Los Filos expansion will also benefit from existing operations and excellent infrastructure. Approximately 51% of the gold production in the life of mine plan is from the CIL plant and 49% is from the existing heap leach facility.”

Woodyer added the company was now putting the study findings into its “overall corporate business model for planning and corporate financing purposes”, but he said it was “obviously a project we should undertake”.

Bermejal Underground

Bermejal underground mine design and cost estimation was completed by SRK Consulting. A total of 11 km of horizontal and vertical development was planned during the initial development period and a further 45 km over the life of mine. The mine life extends for nine years producing 6.4 Mt at 6.57 g/t for contained gold of 1.348 Moz.

Mining costs of $99/t were based on contractor mining, with the mining method being underhand drift and fill with cemented rock fill (CRF) used as backfill. Bermejal underground will have a dedicated CRF production plant. The production rate averages 2,000 t/d and peaks at 2,150 t/d. Bermejal underground contributes 31% of the contained gold in the life of mine plan.

Los Filos Underground

The Los Filos underground mine is currently operating at over 1,800 t/d and, in the life of mine plan, averages 1,700 t/d with mining costs of $73/t based on owner and contract mining. Reduced operating costs, improved mining efficiencies and additional drilling have enabled the update of the Los Filos underground mine plan to extend to 2021. The reserves are 1.9 Mt at 5.50 g/t for a total of 338,000 oz.

Open-pit mining

Los Filos uses conventional open-pit mining methods with an owner-operated fleet supplemented with rental of additional equipment during peak production periods. The average open-pit mining costs are $1.41/t mined.

Los Filos Open Pit

The expanded Los Filos open pit has a proven and probable reserve of 42.7 Mt at 0.57 g/t containing 776,000 oz. The mine life was extended seven years to 2027. The Los Filos open pit has an overall strip ratio of 4:1

Bermejal and Guadalupe Open Pits

The Bermejal and Guadalupe open pits have been split into two open pits and rescheduled to mine the higher-grade Guadalupe ore earlier in the schedule, which significantly improves the economics, according to Leagold. Guadalupe has a proven and probable mineral reserve of 26.3 Mt at 1.55 g/t Au for 1.313 Moz. A pushback in 2020 will open this up as a separate open pit that has a 10-year life, Leagold says. The Guadalupe pit has an overall strip ratio of 8:1.

The Bermejal open pit extends for at least five years to 2025 based on the current reserves. Proven and probable mineral reserves are 34 Mt at 0.54 g/t Au for 588,000 oz. The overall strip ratio of the Bermejal open pit is 2.7:1.

CIL and heap leach processing

The CIL plant is expected to achieve higher recoveries (an average of 89.7%) and better financial returns than heap leach processing for the underground ore and the higher-grade portion of the open-pit ores.

“The plant also provides the ability to process some ore types that were previously not included in reserves as they were not amenable to heap leach processing; this includes material with an elevated sulphur content which exhibits lower gold recoveries at the crush sizes typically used in crushing for heap leach processing,” Leagold says.

The plant is predicted to process a total of 12.4 Mt at an average grade of ore feed of 4.63 g/t Au with an average recovery of 89.7% to produce 1.658 Moz gold.

The expansion feasibility study contemplates the existing heap leach facility continuing to operate throughout the full life of mine plan. A total of 95.6 Mt of ore with an average grade of 0.79 g/t Au will be placed on the leach pads and have an average recovery of 61.9% to produce approximately 1.5 Moz of gold.

Secondary recovery is expected to contribute an additional 111,000 oz from surface re-leaching and re-handling of previously leached ore, Leagold says.

Contributions to the gold production in the life of mine plan are 51% from the CIL plant, 46% from the heap leach and 3% from secondary recovery.