Tag Archives: block cave

OZ Minerals Carrapateena debottlenecking accelerates with HIGmill addition

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OZ Minerals’ Carrapateena operation in South Australia is gaining momentum with its processing plant running in excess of nameplate through a cost-effective and efficient debottlenecking strategy.

The latest sign of this strategy taking shape comes in the form of the installation of a second HIGmill from Metso Outotec.

This high-intensity grinding mill has been installed in parallel to the existing mill at the copper-gold operation to increase regrind capacity for all ore types to maintain optimal concentrate grades, the company says.

“We selected HIGmills due to the simplicity of installation and the total cost of ownership,” the company told IM. “As both HIGmills are identical, this allows for commonality of spares and predictable operation.”

The initial processing plant at Carrapateena was designed to produce at a nameplate of 4.25 Mt/y, yet, through debottlenecking and continued process improvement, the plant has recently run at annualised run rate in excess of 5 Mt/y, the company said. This is also an increase on the 4.6 Mt/y processed in 2021.

Like other ‘connected’ equipment within the Carrapateena processing plant, the new HIGmill has been fully integrated into a SCADA system monitored by the control room. It can also be monitored remotely at OZ Minerals’ Adelaide remote operations centre, the company added.

Beyond debottlenecking, OZ Minerals is planning a major expansion at Carrapateena through the development of a block cave operation, which was signed off by the OZ Minerals Board in early 2021.

The expansion, which will involve converting the lower part of the current sub-level cave into a series of block caves, is expected to prolong operations at the copper-gold mine, while boosting production to 12 Mt/y. This will see average copper production come in at 110,000-120,000 t/y and gold output average 110,000-120,000 oz/y from 2026, compared with production of 55,262 t and 89,778 oz, respectively, in 2021.

Under the expansion project, the company is targeting block cave 1 to begin operations by 2026 and block cave 2 by 2038.

While the block cave is being established, a second process plant will be built in parallel to the existing one. Below surface, construction of the second crusher is expected to be completed towards the end of next year, and processing plant optimisation is ongoing. These will help produce a concentrate to be transported to port and subsequently to smelters by ships, the company told IM.

New Gold to collaborate with MineSense in underground ore sorting move

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MineSense is gearing up for a move underground with the help of New Gold and its New Afton gold-copper mine in British Columbia, Canada.

The Vancouver-based technology company has already established and proven its ShovelSense technology for the open-pit mining sector, with its X-ray Fluorescence (XRF) sensor-based system now operating on shovels, wheel loaders and excavators on a commercial basis across six operating mines. This includes large installations at Teck’s Highland Valley and Copper Mountain’s copper operations in BC, as well as one ShovelSense unit at the Antamina copper operation in Peru.

Designed for operation in extreme environments and retrofits on any existing mobile equipment, ShovelSense units come equipped with a human machine interface and proprietary algorithms that measure and report ore grade/characteristics. They can also connect directly to fleet management or other existing control software systems, enabling mine operators to reconcile geological block models with actual ore grade data.

Having finetuned the system for above-ground operations, the company is now embarking on its underground move, according to MineSense President and CEO, Jeff More.

A trial of the underground ShovelSense system at New Gold’s New Afton mine is first up to complete product development. The company will be installing a unit on a Cat R1600G LHD for this step. This will be followed closely by installation at a “large entity” in Chile – with More anticipating start up in the September or December quarter.

The development agreement with New Gold at the BC-based mine is looking to trial and finetune the system for underground operations, with More confident the ShovelSense system will stand up to the test.

“The core technology – all of the algorithms, software, hardware – is the same as ShovelSense for open-pit mining,” More said. “It is the ‘application package’ – looking at how we can attach the unit to the machine and protect it in an underground environment – that is what we have to test out. The design for this is already complete; it’s just a matter of trialling it.”

New Afton represents a good test for the system.

New Afton is Canada’s only operating block cave mine, with the New Afton deposit part of a larger copper-gold porphyry district in the region. The operation regularly mines 15,000-16,000 t/d of ore and waste, with the majority of this currently going to the mill.

The company has already pursued “ore segregation” projects to boost the grade of material being fed through to the processing side, but the move into the higher-grade C-Zone in 2023-2029 will place an even greater emphasis on ore/waste boundaries and milled tonnes at the operation.

At the same time, the ShovelSense deployment at New Afton will represent the first time MineSense has sent a unit into a mine that has so much payable gold, with most operations the company has worked on being primarily base metal-oriented.

In 2020, New Afton produced 64,000 oz of the yellow metal, along with 32,659 t of the red metal.

“This will be the first time we’re touching gold at this level; we have other mines that have payable gold but not at that level,” More explained.

In New Afton’s case, sampling and historical data has proven that the orebody’s copper and gold ratios tend to be consistent and unchanging over the long term. With this knowledge, New Afton has used technology in the past to determine the copper value and make ore/waste production decisions. ShovelSense allows New Afton to move the ore/waste production decision to the drawpoint, according to MineSense. This reduces mixing and blending during the crushing and conveying circuit which can homogenise the material to the point where it is not worth segregating.

Trialling new technology such as this is nothing new for New Afton.

The operation already uses automated loading through Sandvik’s AutoMine solution, is employing electrification with the use of Sandvik and MacLean Engineering battery-powered mobile equipment, and, in the process plant, has Gekko Systems’ highest volume InLine Pressure Jig IPJ3500 to improve gravity concentration.

More says the ShovelSense unit could be in the Cat LHD bucket at New Afton in August, with the machine then going through an above-ground trial ahead of the underground transition at the end of September.

“By early Q4, we should have completed the pilot,” he said.

OZ Minerals Carapateena copper-gold mine ramp up begins

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OZ Minerals says it has now produced its first saleable copper-gold concentrate from the Carapateena underground mine, in South Australia, just over two years since the board approved the development.

The company said the first concentrate had been produced into the pre-filter press feed tank at the mine, with the achievement meeting the December quarter 2019 schedule mapped out when Board approval was given in August 2017.

Pre-production capital cost at first saleable concentrate is around A$970 million ($669 million) with 2019 growth capital spend on track for guidance of A$540-$570 million, the company said.

OZ Minerals commented: “Sufficient saleable concentrate is expected to be produced to the filter feed tank over the coming days to then complete our first concentrate press. Over 280,000 t of development ore is stockpiled on the surface as the mine now enters a faster circa 12-month ramp-up towards reaching a 4.25 Mt per annum throughput rate by the end of 2020, dependent upon the cave performing as expected.”

Chief Executive Officer, Andrew Cole, said: “This project began three years ago with initial decline works kicking off in Q3 (September quarter) 2016 followed by Mining Lease approval in April 2018 and first underground development ore in April this year.

“Today’s milestone represents the collaboration, support and hard work of a great many people including our operations and construction teams and the large number of contractors involved.”

He said the company’s key operational focus remains on underground development as the company ramps up the mine.

“The streamlined mine design with an expanded footprint will improve cave establishment, reduce risk during the ramp-up phase and may enable future annual throughput expansion opportunities as we continue to assess options to expand capacity above 4.25 Mt annually,” he said.

The company said this ramp-up period would allow it to test and optimise the plant throughout the first half of 2020 leading to gradual throughput and recovery increases to drive progressively higher output in the second half of the year. The now larger sub-level cave footprint along with an optimised mine design is expected to enable a faster cave ramp-up, provided the cave performs as modelled, the miner added, explaining that this would see the target 4.25 Mt/y run rate reached by end-2020 and the potential for a throughput boost.

Cole concluded: “Although we announce first saleable concentrate today, we have already commenced a block cave expansion scoping study looking at increasing both the life and production capacity of Carrapateena from 2025.”

Capital expenditure in 2020 will include permanent mine development, the circa-50 km Western Access Road construction and completion of conveyor installation and crusher, OZ said.

Production for 2020, as the ramp up progresses, is expected to be in the range of 20,000-25,000 t of copper and 35,000-40,000 oz of gold.

Major Drilling helping narrow down Oyu Tolgoi orebody

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Major Drilling says it is nearing the completion of a cave tracking system installation at the Turquoise Hill Resources and Mongolia government-owned Oyu Tolgoi copper-gold mine, in Mongolia.

In early 2000, Major Drilling established a drilling campaign in the middle of the Gobi Desert, with operational supplies needing to ramp up to support 20 rigs that were transported to the site.

This drilling work has since evolved into the tracking system that has proven successful in the block cave operation.

These trackers are lowered through a specially-drilled borehole into the Oyu Tolgoi orebody below. Block cave magnetic beacons are embedded into the orebody and spun to create a magnetic field.

“Magnetisation has been found to be the most effective way to track the fragmentation as an orebody caves in allowing loaders to mine the ore from draw points deep underground,” Major Drilling said.

Major Drilling’s teams strategically place magnetic beacons throughout the mine to create a 3D map and to track the position of the orebody cave-in flow. The cables are attached to the duct rodder, which is lowered from a winch system. Once the trackers are placed, block caving techniques will undercut and fragment the deepest points of the geology, according to the company. The orebody is then collected and taken away for processing.

“Block caving is a low-cost mining method used for the development of massive ore deposits,” Major Drilling says. “Mine planners often use an experienced specialised drilling company to precondition the block cave mining area through hydrofracking. Tracking the flow of the fragmented, caved ore is a critical part of accessing targeted orebodies.”

Mine planners use the information from the magnetic tracking devices placed by the Major Drilling team to understand the direction of intended failure the stone is moving.

Shaun Hogan, Major Drilling’s Project Manager at Oyu Tolgoi, said: “We are nearing the completion of the cave tracking system installation at Oyu Tolgoi. Over the past two years, we have worked very closely with our client and various stakeholders; this partnership has achieved a successful deep tracking network.”

In addition to block cave tracking, Major Drilling also performs seismic monitoring to help predict rock mass instabilities. Seismic monitoring is another specialised drilling service that makes large-scale block cave work safer and more productive.

Major Drilling was awarded the Rio Tinto Growth & Innovation Group Award for the successful seismic drilling program at Oyu Tolgoi in 2017.

thyssenkrupp and Northparkes collaborate on latest crushing innovation

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thyssenkrupp Industrial Solutions Australia says it recently signed a contract that will see the world’s first “double-mouth” jaw-gyratory crusher supplied to China Molybdenum majority-owned Northparkes underground copper-gold mine in New South Wales.

The new crusher has been developed in consultation with Northparkes to meet its specific operating objectives, according to thyssenkrupp.

The company explained: “This unique jaw-gyratory crusher is a modern machine based on the proven BK 63-75 design. thyssenkrupp has developed a new, patented, spider to give the opportunity to feed the crusher from both sides – the “double mouth” jaw configuration, thus removing the need for a primary crusher feed (buffer) hopper and primary apron feeder.”

This dramatically reduces excavation requirements in an underground operation like Northparkes leading to a sizeable reduction in installation cost, according to thyssenkrupp.

The delivery of this latest crushing innovation follows the recent release of the company’s Eccentric Roll Crusher, the modular Variopactor impact crusher and the KB 63-130 gyratory crusher, the company said.

Northparkes is one of the most modern underground block cave mines in the world, with the majority of its loading and haulage operations carried out autonomously. Mining started up at Northparkes in November 1993, with 80% owner China Molybdenum now processing around 6.4 Mt/y of ore of high-grade copper-gold concentrate, which is shipped to its clients overseas for smelting.

Northparkes was the first mine to use the standard indirect fed Jaw Gyratory crusher type BK 63-75 for its newly developed block caving mine concept, thyssenkrupp said, with this primary crusher design becoming the “state of the art solution for block caving mines”.

Ian Smith, Engineering Superintendent of the E26L1N Block Cave Mine project at Northparkes, said: “As a long-time owner, operator and maintainer of the thyssenkrupp jaw gyratory crushers for primary crushing underground, Northparkes is pleased to be installing its third BK 63-75 in the new E26L1N block cave mine underground crusher station.

“The first BK 63-75 crusher of its kind was commissioned underground at Northparkes in 2003 followed by a second installation in 2009. Northparkes has worked closely with thyssenkrupp over the years to develop and make improvements to these crushers and has developed great confidence in the reliability and robustness of the BK 63-75 crusher.”

Smith said the first two crushers installed are of a single mouth design with the latest crusher being a double mouth design that is “ideal for our direct tip underground crushing station dump pocket that negates the use of a large run of mine bin and primary feeder thus reducing the mass excavation underground”. He said the ability of this crusher to handle a very large feed size and a high reduction ratio has also negated the need for the use of a pre-screening grizzly.

He concluded: “Northparkes’ innovative culture is again highlighted as shown in their initiation and involvement in the development of the double mouth feed shell with thyssenkrupp with the aim that the performance of this crusher will not only meet but will exceed expectations.”

Orica keen to collaborate on path to blasting automation

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Orica’s Angus Melbourne told a packed Austmine 2019 crowd in Brisbane this week that the blasting specialist is committed to developing automated solutions for both the underground and surface mining sectors and is working with both customers and industry partners to make this aim a reality.

During his speech on Wednesday, Melbourne, Orica’s Chief Commercial and Technical Officer, walked delegates through a number of achievements the company had achieved over its 140-year history, but also looked ahead to how Orica is focused on revolutionising the drill and blast operations of the future.

“Blasting is one of the few processes in the mining value chain that remains largely untouched by automation,” Melbourne said. “As mines go deeper and orebodies become more remote, the case for blasting automation becomes clearer.”

Among a number of benefits of blasting automation were the ability to remove people from harm’s ways, grant access to difficult ore reserves and reduce operational delays, he explained.

“Due to the complexities associated with a typical blast operation, this is no trivial endeavour,” he said.

Melbourne said progress was already being made with Orica’s automation efforts, singling out its Orica’s WebGen™ wireless initiation technology, in particular. Launched in 2018, WebGen improves safety by removing people from hazardous situations and enhances productivity through the removal of constraints previously placed on operations by wired connections.

“Since its release, more than 130 WebGen wireless blasts have been executed globally across four industry segments,” Melbourne told delegates.

Newmont Goldcorp’s Musselwhite mine has been an advocate of the wireless initiation technology, recently saying the blasting tests it has carried out at the Ontario mine were “a decisive step on the path towards full automation of drill and blast operations in the future”.

The wireless initiation technology is leading to the development of new blasting options, according to Melbourne, who said, in the last 12 months, Orica has co-developed more than seven new techniques that are “revolutionising the way our customers are planning and executing their mining operations”.

On stage, Melbourne then played a short video from CMOC Northparkes in New South Wales, Australia, a miner that recently converted its entire sub-level cave copper mine to WebGen wireless initiation blasting; an Australia and world first, according to Melbourne.

He said Northparkes has seen significant improvements in safety, productivity and ore recovery since the transition. Melbourne’s words were echoed later that day when Orica received the Austmine METS Innovation Award for the use of WebGen at Northparkes.

Melbourne pointed to a second collaborative development that was helping shape the company’s blast automation efforts during his time on stage; this time with an original equipment manufacturer.

The company has been working with MacLean Engineering out of Canada to test the first fully-mechanised drawpoint hang-up blasting solution, he said.

Capable of drilling and charging up to eight blast holes remotely, the solution is underpinned by WebGen wireless technology and, once again, removes people from harm’s way.

“Hang-up blasting is a major issue for block and sub-level cave mines around the world,” Melbourne said. “In fact, at any one time, up to 30% of all drawpoints can be unavailable due to oversize material. All current solutions are either high risk mining activities or are highly inefficient to implement.”

He then played a video highlighting this industry-first solution, before remarking: “This is a significant step towards fully-autonomous production in underground mines. It’s an exciting time for everyone involved and is just one example of an industry collaboration to deliver blast automation.”

Melbourne concluded his presentation by saying, in the future, integrated, automated and intelligent systems will deliver the critical data necessary for executing real-time change and quantifiable impact on all parts of the value chain “through an ‘ecosystem of insight’ never seen before in mining.

“To capture the full potential of rapidly-evolving technology will require new ways of thinking, new ways of working, and a new spirit of collaboration across the industry.”

SolGold outlines new copper-gold-silver block cave mine plan at Alpala

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SolGold has laid out plans to develop a mine at its majority-owned Alpala copper-gold-silver deposit, in northern Ecuador, that will use block cave mining methods applied over several caves designed on two vertically extensive lifts.

The preliminary economic assessment on Alpala estimated a pre-production capital expenditure of $2.4-2.8 billion for a mine that could produce 150,000 t/y of copper, 245,000 oz/y of gold and 913,000 oz/y of silver in concentrate over the life of mine.

The PEA stated a post-tax net present value (8% discount) of $4.1-4.5 billion based on an average $3.30/lb ($7,275/t) copper price, $1,300/oz gold price and $16/oz silver price depending on a 40-60 Mt/y throughput rate.

As part of the PEA, four mine production cases were pre-selected and assessed. This included a 40 Mt/y option over a 66-year mine life, a 50 Mt/y blueprint with a staged ramp up and a 57-year life, a 50 Mt/y fast ramp-up plan with 55-year life and a 60 Mt/y route with 49-year life.

Unit C1 operating costs over the life of the mine were estimated at $0.90/lb copper after gold and silver credits using the 50 Mt/y, fast ramp-up plan.

Resources scheduled in the PEA block cave designs accounted for 2.4 Bt at 0.54% CuEq ROM grade.

SolGold said the prefeasibility study is expected to be completed in December 2019 with a definitive feasibility study scheduled for completion at the end of 2020.

SolGold CEO, Nick Mather, said: “The unusually low operating costs modelled are due to the relatively soft, fractured nature of the ore, resulting in enhanced caveability, a high degree of fragmentation in the cave and ease of crushing and millability, combined with low hydroelectric (consumption and unit) costs. The overall scale efficiencies also assist in the delivery of modelled low operating costs.”

Metallurgical work at Alpala, which is ongoing, indicates gold contents in the pyrite concentrate will require additional investigation to identify an efficient recovery strategy, SolGold said.

Additional metallurgical work is expected to identify solutions for recovery of gold and copper in the pyrite concentrate along with a sulphuric acid product.

Over the period to the end of 2019 when SolGold aims to complete the prefeasibility study, activities will focus on exploration, a new mineral resource, metallurgy and process design, investigation of further tailing disposal options and incorporation of further geotechnical and hydrogeological data into the PFS basis, SolGold said.

SolGold will also commence permitting and fiscal discussions with the Ecuador Government and financial discussions with third party financiers for SolGold’s share of the project costs following completion of the FS.

OZ Minerals outlines block cave potential at Carapateena copper-gold project

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OZ Minerals’ scoping study on an expansion at the Carrapateena copper-gold project, in South Australia, has shown that converting the lower portion of the sublevel cave to a block cave from 2026 could yield up to 60,000 t/y more copper output at the same time as reducing operating costs.

The Carrapateena sublevel cave is still in the development phase and is expected to hit first production in the December quarter of this year. This project is expected to produce an average of 65,000 t/y of copper and 67,000 oz/y of gold over a 20-year mine life.

The study outlined a more than doubling of mine throughput from 4.25 Mt/y to 10-12 Mt/y from 2026 through the development of the block cave and expanded surface infrastructure. This was expected to cost A$1-$1.3 billion ($704-$916 million) in upfront capital and lead to all-in sustaining costs going from $1.05/Ib ($2,315/t) in the sublevel cave operation to $0.90-$0.95/Ib during block cave operation.

The plan would see OZ Minerals access the higher-grade bornite mineralisation first, via the top-down sublevel cave, followed by a bottom-up block cave, OZ said.

Mine expansion and transition to a block cave would require adjustment to the location of future underground infrastructure below crusher station two, including a change in orientation of the decline, conveyor and ventilation, OZ said. In the current operation plan, this is not due for installation until after 2021.

The materials handling system and crushing infrastructure would require additional drive motors and a faster conveyor system to hit the new 10-12 Mt/y capacity, while there would need to be upgrades to the primary and secondary ventilation systems; electricity and communications infrastructure; and water supply, dewatering and underground facilities.

In terms of the process plant, there would need to be either a new parallel processing plant installed or an upgrade of the current sublevel cave processing plant.

OZ Minerals CEO, Andrew Cole, said: “The Carrapateena Block Cave Expansion work showed the conversion to a block cave to be the most value accretive next step for the Carrapateena resource and conceptually for the entire province, as it potentially enables a series of future add-on block caves, which themselves will now be the subject of a Carrapateena Life of Province Plan scoping study.”

He said the sublevel cave construction project remained on schedule for first production later this year, with ramp up to full production of 4.25 Mt/y taking place over the following 18 months.

The company will now move onto a prefeasibility study for the block cave expansion plan, which is expected to be completed by mid-2020.

Factoring in the scoping study results increases life of mine tonnes from 84 Mt at 1.8% Cu and 0.7 g/t Au, to around 145 Mt at 1.2% Cu and 0.5 g/t Au over a 20-year period.

New Gold after different funding strategy for C-Zone block cave at New Afton

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New Gold has launched an internally-funded strategy for the development of another block cave at its New Afton gold-copper mine in British Columbia, Canada, as it looks to extend production through to 2030.

While further details of the strategy are expected later in January, a 2016 feasibility study on the C-Zone implied another 25 Mt of gold and copper ore reserves, equivalent to five years of mine life, could be added through the development of the new block cave.

Early last year, the company decided to defer development of the C-Zone in 2018, electing to evaluate opportunities “that have the potential to further optimise the C-Zone project”. Some of the opportunities identified, which were not featured in the feasibility study, included different tailings options (such as dry stack or thickened/amended tailings), as well as mining approaches based on operating experience in the B-Zone (including reassessing the amount of required underground development in the cave as well as optimising draw bell and pillar designs).

New Afton is a block cave mining operation able to produce 4 Mt/y of copper-gold ore for processing in a flotation plant. The deposit has been partitioned into three zones. The two nearest the surface cave readily and provide the initial mine production, while the deeper block is expected to require assistance in cave development.

An undercut and extraction level has been developed at each block, with ore hauled to ore passes and dropped to a tramming level for transport to the crusher. Ore from the deeper block is hauled by 50-t truck to the crusher level, from where it is conveyed to the mill via a 4.5-km long conveyor system.

Since the start of the current underground block cave operation in July 2012, exploration at New Afton has focused on extending the mineral resource below the current B-Zone block cave reserve. This work has resulted in the development of the C-Zone mineral resource, which was stated as 18.3 Mt at 0.8 g/t Au, 2.2 g/t Ag and 0.95% Cu as of December 31, 2017.

While investors will await further news of the internally-funded strategy for the C-Zone, the existing mine exceeded guidance in 2018. It produced 18,778 oz of gold in the December quarter for 77,329 oz in 2018, above expectations. Copper output also toppled expectations, with 20.8 MIb (9,435 t) and 85.1 MIb for the quarter and year, respectively.

And expectations are for these positive results to continue into 2019.

New Gold said in the December quarter results release that it had started an “ore segregation” strategy during the quarter, which has been further enhanced with the recent commissioning of an ore scanner. This is expected to increase overall mill grade, New Gold said.

Also, during the quarter, the initial phase of a two-phase mill upgrade to address supergene ore recovery was completed on time and on budget. This included the installation of pressure jigs and a magnetic separator with commissioning currently underway.

The second phase of the planned upgrade will be launched during the current quarter, with commissioning scheduled for the September quarter, the company said.

Resolution copper mine looking to automation, Rio says

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The partners at the Resolution copper project in Arizona, US, are likely to look to automation to solve the problems that come with operating at depths up to 2,100 m and temperatures in excess of 70°C, according to a member of Rio Tinto’s Growth & Innovation team.

Rob Atkinson, Head of Productivity & Technical Support for Rio’s G&I team, said operating at such a depth meant it really had to be “a fully autonomous mine”.

Resolution is a joint venture between Rio and BHP, with the former owning 55% and the latter 45%.

The proposed block cave hosts one of the largest undeveloped copper deposits in North America, with a 1.79 Mt resource grading 1.54% Cu. When up and running, it is expected to operate at a rate of around 120,000 t/d, producing some 1,000 MIb/y (453,592 t/y) of the red metal. This would make it one of the biggest copper mines on the continent.

But, to get to this orebody, one of the deepest single-lift shafts in the US had to be sunk at No 10 shaft (7,000 ft or 2.1 km).

While sinking this, Cementation USA came across huge inflows of water and rock temperatures of up to 80°C, making excavation particularly tricky.

This is why haulage in the mine is likely to be carried out by autonomous equipment. According to a 2017 interview with then Vice President of Operational and Technical Support for Rio Tinto’s Copper & Diamonds business, Craig Stegman, autonomous LHDs could also potentially feed an autonomous ore handling system at the underground mine.

And, in addition to this, there is also the possibility of using battery-powered LHDs at the operation.

Stegman, at the time, said Rio was working with suppliers such as Caterpillar, Sandvik and Komatsu to create an alternative to vehicles that were tethered to an electrical connection.

The deposit, located 96 km east of Phoenix, near the town of Superior, is still some way off being exploited.

The Resolution Copper joint venture (55% Rio Tinto, 45% BHP) confirmed back in June that rehabilitation work at its No 9 Shaft was on track for completion in 2019. This shaft would then have to be deepened and connected to No 10 Shaft in 2021.

While the mine is likely to be autonomous, the operation is expected to employ some 1,400 direct employees as well as a further 2,300 contractors and other support roles, according to Rio.