29 November 2014
|Newmont's million ounce monster|
|Thursday, 26 November 2009|
ONE million ounces of production a year will make Newmont Mining’s Boddington mine the largest gold mine in Australia, and with costs forecast at $US300 an ounce it will also be one of the lowest-cost. It is even more impressive considering the project was on care and maintenance for most of the past decade and the deposit grades around 0.9 grams per tonne gold. Kate Haycock visited the newly commissioned mine.
|Newmont Mining's Boddington copper-gold mine, 130km south of Perth, featuring a Bucyrus shovel and Cat 793D haul trucks.|
|Newmont's Boddington gold mine.|
|Ore stockpile at Newmont's Boddington gold mine.|
|The Residue Disposal Area at Newmont's Boddington copper-gold mine, 130km south of Perth.|
With production forecast to reach full capacity midway through next year, the Boddington gold development is one of the most impressive success stories of the Australian gold mining sector.
The project, 130km southeast of Perth in the Peel region, will produce 1 million ounces per annum during its first five years of operation.
It will also produce around 30,000 tonnes of copper each year from exports of 200,000-220,000tpa of copper concentrate.
The project has an estimated mine life until 2034 from gold reserves of more than 20 million ounces.
The project’s scale is vitally important considering the low grade of the gold mineralisation at the Boddington deposit, which averages around 0.9 grams per tonne gold.
Some 120 million tonnes of rock will be shifted each year to produce around 35Mtpa of ore by a mining fleet of more than 30 Caterpillar 793D trucks working in tandem with three Bucyrus electric rope shovels and one Terex hydraulic shovel.
Boddington has been a big investment for Newmont with almost $US3 billion spent on re-developing the operation, but it will pay off relatively quickly.
Boddington general manager of operations Jim Beyer said the project would produce around $1 billion in gold revenues each year depending on the gold price.
Gold will account for around 80% of Boddington’s revenue each year, although this proportion will fluctuate on gold and copper grades and prices.
“Copper is a very important part of our revenue stream and it helps offsets our costs which is one of the reasons why we are a low-cost gold producer,” Beyer said.
Boddington’s costs applicable to sales have been forecast at around $US300 an ounce.
Beyer also said the gold price would have to be a “lot, lot lower” to make production uneconomic, even despite the low grades of the project and the rising Australian dollar.
“This project was justified on prices more like $US500-600, but also more favourable exchange rates for us,” he added. “Certainly not $US93c.”
Beyer told journalists onsite at Boddington this week that the copper operation was too small to justify a standalone electro-winning plant for concentrate, which will instead be shipped directly to customers including Asian companies.
Newmont has been stockpiling copper concentrate – which also contains around half of the gold produced at Boddington – since production began earlier this year and expects to ship its first parcel of concentrate this week.
The other half of the gold produced at the operation will go to the gold room to produce gold dore bars.
Apart from its size, Boddington also stands apart as an example of Newmont’s investment in technical innovation.
One area where the company has been leading the field is in the implementation of high-pressure grinding rollers.
Boddington has “very hard rock,” Beyer explained, and with such a high work index, rock breaking takes a lot of energy. HPGRs use less energy than other rock-breaking methods like semi-autogenous mills.
“We had to look at different ways of breaking the rock,” he said.
“They are two massive steel rollers that are probably 1.8 metres across and 2 metres in diameter. They roll together and you drop the rock between them.”
The HPGR technology has been used in the cement industry and in diamond mining, and was installed at Freeport-McMoRan’s Cerro Verde copper mine in Peru.
Beyer said the company had learned a lot from the experiences at Cerro Verde and Boddington had benefited from the steep learning curve at the mine.
So far, Boddington’s four sets of Thyssenkrupp-Polysius HPGRs have been working extremely well.
“We’ve been very happy with their performance,” Beyer said.
The HPGRs complement a pair of 60x110 primary crushers, and five Nordberg MP 1000 secondary crushers.
The plant also has four balls mills with the largest twin pinion drives produced to debate, supplied by Finnish company Metso.
In other areas Boddington is also setting an example for the rest of the gold mining industry, such as its best practice tailings storage.
The Residue Disposal Area, as it is called, cost around $32 million alone and utilises a thick barrier of clay to ensure tailings don’t enter the local waterways, and also boasts a thick plastic lining.
The mine operates in an extremely wet area by Western Australian standards and the RDA was designed to cope with the extremes of wet weather.
The lining is 1.4-1.6mm thick and, according to Boddington’s superintendant of safety, mining and construction Neil Wixon, is very difficult to pierce.
To protect wildlife, corridors have been laid over the rubber lining so if kangaroos or other animals make their way down to the water in the RDA, they can clamber back out.
Wixon also said any animals that drank from the tailings dam would find the water unappetising and would almost certainly not want to continue sipping the tailings, meaning the levels of contaminant exposure would be miniscule.
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