Mining techniques have dramatically transformed over many years, with technological advances improving efficiency and the safety and health of our people, while minimising the environmental impact of our operations. NSW has both open-cut and underground mines.
Open-cut mining usually happens where mineral deposits are close to the surface. It involves blasting and removing surface layers of soil and rock to reach the mineral deposit. When the mineral seam becomes exposed, it is drilled, fractured and the mineral recovered for processing. Open-cut mining can be more effective than underground methods, generally recovering 90% of a mineral deposit, and accounts for about 65% of raw coal production in NSW. Open-cut mining is also used for some gold and copper production in NSW. One of Australia’s largest open-cut coal mines, BHP Billiton’s Mt Arthur Coal mine, is located in the Hunter Valley.
Underground mining involves creating tunnels from the surface into the mineral seam, which can be hundreds of metres below the surface. These tunnels are used to transport machinery that extracts the mineral. Underground mining accounts for 60% of world coal production, but is less common in NSW, making up around 35% of raw coal production. This method is also used to mine metallic minerals like gold and copper. The two main types of underground mining in NSW are bord-and-pillar and longwall mining.
Bord-and-pillar: Bord-and-pillar, or room-and-pillar, is the oldest underground mining technique and was common in NSW before longwall mining began in the 1960s. This method uses a grid of tunnels and involves progressively cutting panels into the coal seam whilst leaving behind pillars of coal to support the mine. This method has been in steady decline as more efficient technologies are introduced, but is still used in a small number of mines across the state, like Yancoal’s Tasman Mine near Newcastle.
Longwall mining: Longwall mining revolutionised underground coal mining with its capacity for safe, cost effective and efficient large-scale extraction. Longwall mining uses mechanical shearers to cut coal away whilst hydraulic-powered supports hold up the roof of the mine. As coal is removed, the supports are moved forward and the roof is collapsed behind them, which can result in subsidence. Longwall mining is more efficient than bord-and-pillar as it does not leave behind pillars of coal, so more of the mineral resource can be extracted. One example of a longwall mine is Centennial Coal’s Angus Place mine, near Lithgow.
A newer technique is block-caving, where mineral ores – like gold and copper - are extracted by collapsing the mineral deposits under their own weight. Australia’s first block cave mine opened in 1997 near Parkes, in Central West NSW. Located at Northparkes Mines, it is part of Rio Tinto’s Mine of the Future program, which aims to make mining more efficient and safer through increased automation and remote operation.
Coal preparation & minerals processing
Coal direct from a mine has impurities like rocks and dirt that are removed through washing and treatment at a coal preparation plant. Coal preparation makes the resource more profitable by improving its quality and also lowers transport costs by reducing waste products.
Coal preparation also minimises the impact on air quality during transportation of coal to power stations or our export ports in Newcastle and Wollongong.
Minerals processing encompasses a range of activities including exploration, mining and manufacturing of resources. NSW leads Australia in minerals processing, with substantial infrastructure in steel, aluminium and cement production, as well as refractories used to produce a range of materials like linings for furnaces, kilns and incinerators.