A deep recession and volatile mineral prices have put pressure on mining companies to explore further and deeper than ever before in search of new revenue streams. But as well as investing in new projects, companies are also ploughing billions into operating and improving the infrastructure it takes to maximise huge, well-established deposits.
Here we venture into a world of epic equipment and mind-boggling statistics to check out some of the highest-yield mining operations in the world.
Grasberg gold and copper mine, Indonesia
Located in remote highlands of the Sudirman Range in the province of Papua, Indonesia, is Grasberg, the world's largest gold mine and second largest copper mine. Freeport began its operations in 1990 and has progressively extended exploitation to three mines: the Grasberg open pit mine, the deep ore zone (DOZ) underground block cave, and the Big Gossan open stoping mine, the latest addition at the end of 2010.
Grasberg's open pit operations produced more than 67 million tons of ore in 2006, providing more than 75% of the mill feed. In 2011 however, Grasberg has been operating at minimum production since 12,000 of the 23,000 workers went on strike in September to demand higher pay.
The stoppage has led Freeport to declare 'force majeure' on exports and Barclays Capital has forecast the global copper mine supply to fall 2% this year - the first production drop since 2002. It is also questionable if Freeport can meet its 2011 fourth-quarter output and sales targets.
Production is nevertheless expected to continue through to mid-2016 and by then underground mining operations are scheduled to start at the Grasberg block cave mine, which is currently in development. The mine's milling and concentrating complex is also one of the largest in the world, with four crushers and two giant semi-autogenously grinding units processing about 240,000mt of ore daily.
Production at DOZ is expected to continue through to 2019 and Freeport plans also to ramp up production at the deep mill level zone (DMLZ) block cave mine in 2015.
Bingham Canyon copper mine, US
The Bingham Canyon Mine near Salt Lake City in Utah, owned by Rio Tinto and operated by its subsidiary Kennecott Utah Copper Corporation, is not only one of the US' oldest working mines (marking its 100th year of operation in 2003), it is also one of the country's biggest copper producers. Its 300,000t of annual output supplies 18-25% of US copper requirements.
The open-pit mine is also the largest man-made excavation anywhere in the world, according to Kennecott, measuring nearly three miles across and three quarters of a mile deep, with the company estimating that a further 800ft will be excavated by 2018.
Bingham Canyon also provides an interesting illustration of the impact that changing mineral prices can have on mining operations.
The plant currently produces around 30 million pounds a year of molybdenum, an element that has become increasingly important for Kennecott due to rising demands.
The company made $30 million from molybdenum sales in 2002, but income has shot up alongside skyrocketing prices, with more than $700m brought just three years later.
This, combined with the discovery of a large molybdenum deposit (made possible by analysing 70s-era drill logs with modern data processing and visualisation technology), will likely see molybdenum form an ever greater part of Bingham Canyon's future production.
Black Thunder coal mine, US
One of the main competitors in the race for the worldwide biggest coal mines is Arch Coal's Black Thunder thermal coal mine, located in the Southern Powder River Basin of Wyoming, US, which contains one of the largest deposits of coal in the world.
Opened in 1977, it is still the largest single coal mining complex in the world and the first one to ship one billion tons of coal, providing around 10% of the US coal supply today.
The mine produces low-sulphur, sub-bituminous coal, suitable to fuel power stations without any preparation other than crushing. In 2007, the mine produced around 86.2 million tons of coal, which is nearly 20% of Wyoming's total coal production and higher than in 23 other individual coal producing states.
In 2010, this number rose to 116.2 million tons of coal, with the company claiming to produce 'the energy equivalent of one million barrels of crude oil every day'.
Black Thunder coal mine operates several individual open pits, using six large draglines for overburden handling. Two of the draglines are among the largest in the world, weighing 14.7 million lbs at a height of 238ft, and are able to carry up to 164yd³ of material at once.
The mine also operates 22 massive shovels that are able to dig up 120t in a single bucket, as well as 150 haul trucks that operate continuously at the mine.
Goro Nickel project, New Caledonia
The tiny archipelago of French dependent territory that is New Caledonia might be home to only one major city and a population of little more than 250,000, but it also hosts one of the world's largest mining projects under construction. The Goro Nickel project, the main shareholder of which is Vale Inco, has been producing nickel and cobalt from the Goro plateau since 2010, gradually ramping up until full-capacity production is expected to begin in 2013.
Once in full swing, the Goro Nickel project is expected to produce 60,000t of nickel and up to 5,000t of cobalt from proven and likely reserves of 120 million tons, representing a massive 20% share of global supply.
Despite the huge reserves waiting to be tapped, the project has been inundated with delays and budget increases. Vale Inco and its partners are now two years behind the original schedule and nearly $2bn over the initial budget (total cost estimates were recently revised from $3.2bn to $4.3bn).
Many of the project's problems have been a result of deteriorating relations with local groups over the environment and sustainability issues.
The start of production at the project was delayed from late 2008 to 2010 after the construction of an offshore tailings pipe was delayed by complaints from local community groups. Most notable of these is Rhéébù Nùù, an organisation of indigenous Kanak people established to monitor the Goro project, which released a damning statement saying: "The Goro Nickel project does not fulfil the conditions of respecting the environment and even less the conditions for sustainable development".
With the project rapidly losing friends in New Caledonia, further delays could put Vale Inco's proposed 2013 full-production date in danger.
Chuquicamata copper mine, Chile
To date the biggest open bit copper mine by digged volume is Chuquicamata. Located 1,240km north of the Chilean capital Santiago, the open pit mine is owned and operated by Chilean state company Codelco and includes Radomiro Tomic.
Despite its 90 years of extensive exploitation (operational since 1910,) 'Chuqui' as it is commonly known, produced about 29 million tons of copper by the end of 2007, remaining one of the world's largest copper resources.
The mine's open pit is the world's largest at 4.3km-long, 3km-wide and more than 900m-deep. Chuqui's smelter and electrolytic refinery is, with 855,000t a year, among the world's largest. Apart from copper, the mine is also a significant producer of molzbdenum, a silvery metal often used in high-strength steel alloys.
The Chuquicamata open pit mine is expected to close by 2013. A new underground mine will be developed to 2018 at an estimated cost of $2bn with an expected daily production output of 120,000t copper a day. Sinclair Knight Merz undertook the conceptual engineering of the new underground mine in 2007-2009 and envisages four subterranean tunnels that extend 1,500km under the surface of the current mine. The tunnels will deepen by nearly 787m by the end of production in 2060.
Jwaneng mine, Botswana
Jwaneng is the world's richest and largest diamond mine by output, and it's only going to get bigger. The mine provides around 60-70% of owner Debswana's revenues, with production in the range of 12.5 million to 15 million carats a year.
In December 2010, Debswana (a joint venture between De Beers and the Government of Botswana) embarked on the largest single investment in Botswana's mining history to extend Jwaneng even further.
The $3bn expansion project, called Cut 8, is expected to allow the diamond mine to continue its current production levels until at least 2024 with the extraction of an additional 102 million carats.
Around 1,400 of Jwaneng's 2,500 employees are directly involved with the project, which is in the process of removing 658 million tons of waste material to open up the new deposit.
On top of Cut 8, Debswana is also developing its ongoing Jwaneng Resource Extension Project (JREP) to allow the exploitation of resources at the mine to go deeper as well as wider. JREP's scope involves getting access to indicated resource estimates down to around 850 metres below the surface, maximising the mining output of all Jwaneng operations, including Cut 8.
By Elisabeth Fischer and Chris Lo