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Δευτέρα, 22 Απριλίου 2019

Inside Australia's deepest gold mine — how deep can history go at Gwalia?

The Gwalia gold mine in Western Australia reaches 1,660 metres below the surface.Gwalia is the deepest trucking mine in the world and can trace its history back to the 1890s(ABC Goldfields-Esperance: Jarrod Lucas)



A truck driver working at the bottom of Australia's deepest gold mine gets loaded up with about 55 tonnes of precious cargo — hard rock blasted from the Earth and containing small specks of the yellow metal. For every tonne trucks cart to the surface there might be only seven grams of gold, the equivalent of about one teaspoon.

The mine's name can be traced back to its Welsh heritage with former owners, Sons of Gwalia, translating to Sons of Wales.
Driving at the speed limit of 30 kilometres an hour, it takes drivers just under two hours to make their way to the surface to dump their load and head back down. Today, it is the deepest trucking mine in the world and can trace its history back to the 1890s when former US president Herbert Hoover was mine manager.

This is Gwalia in Western Australia's remote northern Goldfields.

The mine's rich yet bloody history includes the deaths of 83 miners between 1898 and 1995 when 24-year-old diamond driller Graham Martin died on the job.

Today, mining at Gwalia has reached a depth of 1,660 metres below the surface and the plan is to reach 2,300 metres by 2031
Since its discovery in 1896, Gwalia has produced more than 5.5 million ounces — worth about $10 billion at today's gold price — to make it one of the richest gold mines in Australia's history.

The furnace burns at close to 1,000 degrees Celsius.
ABC Goldfields-Esperance: Jarrod Lucas
The mine's name can be traced back to its Welsh heritage with former owners, Sons of Gwalia, translating to Sons of Wales. Sons of Gwalia is now known for one of the biggest corporate collapses in Australian history, with its 2004 demise marked by debts of more than $800 million.

Most gold bars poured at Gwalia are worth about $1 million. The 14,113-gram bar produced was worth about $850,000 at today's prices — good enough to buy a house in Sydney or Melbourne. ABC Goldfields-Esperance: Jarrod Lucas
Since Melbourne-based St Barbara took over ownership and restarted mining in 2008, there have been gold price crashes, skills shortages and a once-in-a-generation mining boom. But it has been a defining decade in Gwalia's history, during which the mine has produced more than two million ounces of gold.

Modern miners reaching new depths. Today, mining at Gwalia has reached a depth of 1,660 metres below the surface and the plan is to reach 2,300 metres by 2031.

Gwalia employs 170 St Barbara workers, mostly on the processing plant, and 430 contractors who take care of mining. Modern mining techniques have replaced the original wooden headframe and shaft, which was saved and now forms part of a museum alongside the old mine manager's accommodation, known as Hoover House. The underground portal which was blasted into the bottom of a giant open pit also bears the name of the 31st President of the United States.

New ventilation to improve conditions for workers. One of the biggest challenges to extend the mine life at Gwalia is to get chilled air from the surface to the miners working below.  That is why $80 million is being spent to improve the mine's ventilation, including sinking large new shafts to reach the deepest parts of the mine. St Barbara managing director Bob Vassie said there was no end in sight for Gwalia.  "This mine made over $250 million last year, so if you're that strong you want to be doing it for longer," he said. "Our previous mine life was only to 2024, and we've been able to extend it out to 2031, but the only way we can do it is by adding more ventilation. "We're already looking at going down to 2,300 metres below surface, so we're setting ourselves up for a long future here."

Precious metal kept under high security. The ABC was given rare access to film a gold pour at Gwalia. The 14,113-gram bar produced was worth about $850,000 at today's prices — good enough to buy a house in Sydney or Melbourne.Most gold bars at Gwalia are typically worth $1 million, with some of the highest purity gold in the country averaging around 92 per cent.  All the bars are shipped off to the Perth Mint for further refining. The jaw-dropping value of the precious metal is underlined by the high levels of security at gold mines. As one worker quipped, $10 million worth of iron ore from WA's Pilbara would take a bulk carrier a few weeks to sail to China, but $10 million of gold could fit easily in the boot of a standard car.  

Golden days at Gwalia far from over.The big question for Gwalia is whether mining can go beyond 2,300 metres? The deepest mines in the world are in South Africa, where shafts are approaching depths of up to 5,000 metres.  Mr Vassie said safety was the biggest consideration in mining deeper. What happens after that [2,300m] is controlled by your mining rate and the design of your workings," he said. "The deeper you get you don't try and open up too long a space before you fill it up, otherwise you run the risk of it collapsing".  "There's a lot of things we can do to potentially go deeper than 2,300m but it might create a change that might drop our mining rate, so they're the sort of things we have to balance.  "A future out to 2031, that's quite a long future in terms of Australian gold mining.  "We're also drilling what we call under the headframe, looking for old historic workings, so we're drilling to look for potential parallel mines where we can use the same infrastructure."