Technology enables penetration of mineral zone discovered 40 years ago

Hopes 'innovative' mining technique can penetrate untapped mineral zone under Broken Hill Thu 6 Aug 2026 at 9:03am In short: A Broken Hill mining company says it has developed a new technique to penetrate a rock deformation protecting a mineral deposit. The deposit was discovered more than 40 years ago and is said to contain potentially millions of tonnes of valuable minerals. What's next? The company believes the deposit could secure its long-term mining future if new drilling results are accurate. A large deposit of minerals was discovered in 1983 under an outback mining city's streets, not far from existing operations. Dubbed the "Centenary Zone" due to its discovery aligning with the 100th anniversary of the city's founding, the then-mine operator was optimistic about what lay below but could not properly access it. Patrick Walta, executive chair of Broken Hill Mines, which took over the mine in 2024, said the operator drilled about 13 holes more than a kilometre long from the surface into the deposit. "[They] managed to hit [the Centenary lode], which ultimately came out as an [estimated] resource of about 5 million tonnes, at eight or nine per cent zinc equivalent," he said. "[But] then you have this shear zone called the Glove-Vauxhall Shear, which is effectively a geological sequence that interrupts everything." A seemingly impenetrable barrier Geologist Sandra Close described a shear zone as a natural deformation of rock that is difficult to penetrate. "[The rocks have] been crushed, they've been pulverised, [it's] several meters thick and very, very difficult to drill," Dr Close said. "If you try drilling them, the drill rods get stuck, and they can't get through, [so] it's never been properly tested in the last 43 years for that very reason." This lode of mostly unknown potential has sat untapped for more than four decades, but that may be about to change. Mr Walta said Broken Hill Mines' geology team came up with a new groundbreaking solution to do targeted drilling beyond the shear zone. "That was by putting in a wide diameter hole [through the shear] and casing that hole [which] allowed them to put smaller daughter holes through [it]," Mr Walta said. "And so, it could get through the shear without interruption [which] was a key development that allowed us to really assess what Centenary actually was." New estimates indicate major potential Mr Walta said the new drilling suggests the deposit is roughly five times as thick as previously estimated. He said it was also almost double the predicted level in the purity of zinc, an anti-corrosive mineral used globally to prevent metals like steel from rusting. "It's clearly going to be much larger than the existing five million tonne resource … if we can get the drill [to] 10, 15, 20, 20 plus million tonnes, it has massive implications for [the company]," Mr Walta said. "[This also] means long-term feed supply to our existing plant, which ultimately means longer-term mining operations occurring in Broken Hill." Dr Close said she was impressed by the geology team's solution to access the Centenary Zone, and was hopeful the company's long-term aspirations would come to pass. But she also said it was too early to say whether this was a guarantee, and finding out would be a costly exercise. "The challenge will be how they can develop through that really nasty ground in the shear [so] they can properly enable equipment to get in there and also ventilation shafts to be developed and that sort of thing," Dr Close said. "So, it's very innovative what they've done, but there's a lot more to go at the moment."