Tag Archives: decline

Barminco starts round one of portal development at Barrick Hemlo

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Barminco says it has mobilised to start the development of the new underground portal at Barrick Gold’s Hemlo gold mine in Ontario, Canada.

The installation of the portal ground support has been completed and a new Sandvik DD421 jumbo is being used to drill the first round of what will be the entrance to the new decline ramp, Barminco said.

It added: “Barminco is proud to be introducing high speed development capabilities at Hemlo, adding value to the already well-established mine.”

Earlier this year, Barminco was issued a letter of intent to provide underground contract mining services at Hemlo following Barrick’s decision to phase out open-pit mining and move to an underground contract mining model at the operation.

Perenti, Barminco’s parent company, said back then that its underground contract mining division would “bring industry-leading technology and productivity to Hemlo in support of Barrick’s goal to modernise and improve the performance of the mine and establish it as a Tier Two asset within its group”.

AngloGold, IGO eye Tropicana production flexibility as Boston Shaker goes commercial

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AngloGold Ashanti, in conjunction with its joint venture partner IGO Ltd, has declared commercial production at the Boston Shaker underground mine at its Tropicana gold operation in Western Australia.

Situated some 330 km east-northeast of Kalgoorlie, the operation is managed by AngloGold Ashanti Australia (AGAA) with a 70% interest, while IGO holds the remaining 30% interest.

Development of the Boston Shaker mine was approved in March 2019, and the mine transitioned into commercial production this month on schedule, below the A$105.7 million ($77 million) budget and, importantly, with no recordable safety incidents, AngloGold said.

Boston Shaker will deliver around 1.1 Mt/y of ore at an estimated grade of 3.5 g/t, contributing some 100,000 oz/y to gold production over a seven-year mine life.

“Underground mining at Boston Shaker will leverage further value from this high performing operation, achieving payback in just over three years with upside potential as the deposit remains open at depth,” AngloGold Ashanti SVP Australia, Michael Erickson, said. “The underground mine will contribute higher-grade mill feed from the current quarter onwards, improving the gold production profile and enhancing cash flow during calendar 2021-2023 when the mine plan includes periods of higher waste stripping in the Havana open pit.”

AngloGold has previously said operational excellence work at the underground mine is focused on remote bogging, the mechanical operator-controlled digging of ore from surface, and on optimising level spacing and extraction ratios.

The first production stope was fired in June 2020 and underground ore production has now reached an annualised production rate of 700,000 t/y with the design production rate expected to be achieved in March 2021.The commercial production milestone at Boston Shaker comes after Tropicana produced its 3 millionth ounce of gold in March this year, just seven years after pouring first gold in September 2013.

AngloGold explained: “From commencement of the operation at Tropicana the mining strategy has been designed to optimise cash flow, net present value and the delivery of ore. The Tropicana, Havana, Havana South and Boston Shaker open pits have been mined as a series of cutbacks, sequenced and scheduled to maximise value at a mining rate that delivers the best mining unit cost for the scale of the operation.”

Up until June 2020, ore production from the open pits exceeded the plant capacity, allowing higher-grade ore to be preferentially treated, while lower grade ore was accumulated on stockpiles. Over the course of the second half of 2019 and first half of 2020, the Tropicana pit and Havana pit were completed, in line with the mine plan. As a result, grade streaming came to an end and stockpiled ore is currently being used to supplement the mill feed from the Havana South and Boston Shaker pits.

A decision was made in the June 2020 quarter to invest in the next cutback of the Havana pit (Stage 2) which will allow access to the deeper Havana open-pit ore from 2022 onwards. While this cutback is being completed, mill feed will be sourced from the Boston Shaker open pit, supplemented by some 4 Mt/y of low grade (0.85-1.05 g/t) stockpiled ore, resulting in a lower milled grade over the period. The lower grade will be partially offset by the Boston Shaker underground mine, which is ramping up and will be contributing at full capacity by the second half of 2021.

The plan remains for gold production (at 100%) in 2020 and 2021 to be between 400,000-450,000 oz, compared with 513,785 oz last year. From 2022 onwards, annual gold production will normalise between 450,000-500,000 oz as the low-grade stockpile ore in the mill feed is displaced by a larger proportion of Boston Shaker underground ore and an increasing contribution of higher-grade ore from the Havana pit, as the cutback progresses.

AngloGold says significant potential remains to unlock known extensions of mineralisation beneath the Tropicana and Havana open pits and the extensions at depth of the Boston Shaker Underground. Development of an underground drill drive from the Boston Shaker Decline is well advanced with a total of 240 m completed to date. The drill drive is well positioned to also provide production access to the Tropicana underground reserve should the drilling prove successful. Underground diamond drilling is scheduled for the December 2020 quarter with a decision to mine expected during 2021.

Final trade-off studies are currently being completed on the Havana Stage 3 open pit cut-back and Havana underground to determine the optimal open pit – underground interface. A decision on the way forward for Havana Stage 3 is expected to be made during 2021.

(photo credit: Macmahon)

NQ Minerals acquires Beaconsfield mine, plots new underground decline

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NQ Minerals has added the historic Beaconsfield gold mine, in Tasmania, Australia, to its growing portfolio, with the London-listed company saying it plans to recommission the processing plant and re-develop the underground mine with a new decline.

The company announced this week that it had signed all necessary agreements and made the necessary payments to purchase and take immediate possession of the Beaconsfield mine.

The mine has historic production of circa-1.8 Moz of gold averaging around 15 g/t to its name, and was closed in 2012 due to the low gold price at that time.

“The gold price has since increased by over 100% and the company plans to re-open the mine as soon as practicably possible,” NQ Minerals said.

The 350,000 t/y processing plant, which is currently under care and maintenance, will be recommissioned as part of this plan.

NQ Minerals strategy for re-opening the underground mine, meanwhile, involves developing new modern mine decline access into the existing Beaconsfield mine from surface to reconnect into the existing mine workings at the lower section of the orebody, which comprises all of the current stated gold resources, the company said.

“This new decline will be capable of running large modern mining equipment and men/materials/rock from surface to anywhere in the mine underground workings and will allow for the most efficient low-cost operations possible,” it said.

The main decline currently in the mine is a 5 m x 5 m access way (running down at an angle of 1 m for every 7 m in horizontal length, pictured) that starts 400 m from surface all the way to the bottom of the mine at 1,200 m from surface, according to a NQ Minerals spokesperson.

“The main shaft that accesses that decline is now out of use and is part of the Beaconsfield Heritage Museum,” the spokesperson clarified.

The plan is to run a new 6 m x 6 m decline from surface (popping out near the processing plant) and connect it to the old decline at 400 m depth at the bottom of the Hart Shaft, according to the spokesperson.

“This way, we can run very large diesel trucks (50 t capacity), large front-end loaders and big drill and blast equipment from surface to anywhere in the mine,” the spokesperson added.

Up until 2012, all the big mining equipment had to be dismantled and taken down the old shaft in pieces and re-assembled at the 400 m depth level before it could get used. This big equipment is still down the mine, according to the spokesperson.

“This old way of getting mining equipment down the mine was very slow and very expensive,” the spokesperson explained.

“The other good thing about a new access to surface is the mine can also have smaller-sized equipment easily moved around the mine for mining of the gold orebody, ie equipment suitably sized for the job it has to do,” the spokesperson said.

“The combination of the above is that this will enable economies of scale and economies of suitability.”

NQ, which is currently increasing production at its flagship Hellyer gold mine in Tasmania, Australia, announced a new JORC-compliant mineral resource estimate of the lower section of the Beaconsfield gold mine of 1.454 Mt grading 10.3 g/t for 483,000 oz of gold, earlier this year.

David Lenigas, NQ’s Chairman, said: “Beaconsfield is an exceptional high-grade gold asset and will provide a solid platform to bring the company’s second mine in Australia into production.

“The company is now focused on bringing the Beaconsfield gold processing plant back into operational status as soon as practicable. The mine has a long and rich history in northern Tasmania, and we understand the importance of this heritage. We are looking forward to bringing jobs and economic activity back to Beaconsfield.”