This article is a sponsored feature from Mining.com.au partner Dart Mining NL. It is not financial advice. Talk to a registered financial expert before making investment decisions.
Dart Mining (ASX:DTM) might be better known as a gold explorer, but the company had antimony in its portfolio long before it was a hot commodity.
There are few primary supplies of antimony in the world, it is commonly a byproduct of gold (and other metals), and until a couple of years ago most people probably never heard of it.
But the commodity has now earned a spot on the critical minerals lists of several countries due to its importance to national security.
Antimony is more commonly known for its use in hardening the lead alloy in bullets, but it also has important applications in electronics, energy storage, flame retardants and even glass. The use of antimony as a clarifier in photovoltaic glass is a rapidly expanding usage as it significantly improves solar cell efficiency.
Dart Mining executive Chairman James Chirnside tells Mining.com.au that with defence expenditure budgets and solar cell usage rapidly rising around the world, antimony demand is increasing in sync, and this is no short-term bubble.
“We see antimony as having long-term demand, slow but increasing supply outside of China, and a greater price stability than lithium,” he says.
The International Institute for Strategic Studies estimates global defence spending rose from US$2 trillion ($3.07 trillion) in 2022 to US$2.46 trillion in 2024 and accounted for nearly 2% of gross domestic product, up from 1.6% two years earlier.
In the past decade, military spending has risen about 37%, according to the Stockholm International Peace and Research Institute.
The US, China, Russia, Germany and India accounted for 60% of the world’s total defence spending in 2024. In recent months, NATO member countries – mainly in Europe – have committed to substantial increases in military spending after pressure from the US. Defence spending is forecast to rise from 2% to 5% of each country’s economic output by 2035.
The strong demand for antimony coupled with the shortage of supply and restrictions on exports from China and Russia – which control most of the mined and refined supply – culminated in the metal hitting over US$60,000 a tonne this year. At today’s refined metal prices 1% antimony is equivalent to over 6% copper.
“Between the two of them, they were probably supplying about 60% to 70% of the world’s demand and so it was a price shock. It had been going up nicely before that anyway, but that kind of put a bit of fire under it,” Chirnside notes.
Dart has an antimony presence at its three main gold projects – Rushworth in Victoria and Coonambula and Triumph in Queensland.
Drilling for early antimony resource at Coonambula
Non-executive director Terry Bates says the antimony uncovered so far at Coonambula is “very high grade”.
“Our intention is to infill drill and declare a JORC resource on antimony and gold as quickly as possible at Coonambula,” he tells Mining.com.au.
“There’s no end of samples from 15% to 45% antimony. It’s basically stibnite, the shoots are virtually pure, it is very high grade, which is why it was direct shipping ore. They didn’t process it, there was no need.
“There are not many direct shipping ore antimony projects around. As recently as 1983, they were taking direct shipping ore out of there with an average grade of 20% antimony.
Coonambula has had limited modern exploration, with no drilling done since 2014. Surface trenching in 2024 returned assays up to 23.9% antimony and 9.93 grams per tonne gold.
The project area encompasses the historical Banshee Antimony Mine, where previous drilling intersected high-grade antimony and gold mineralisation over a 650m strike length, including 3m @ 9.18% antimony, 3m @ 1.5% antimony and 8.53g/t gold from 18m, and 6m @ 5.12% antimony and 1.55g/t gold.
Dart received a $180,000 grant from the Queensland Government to undertake induced polarisation geophysics over the antimony zones and strike extensions at Banshee to refine drill targeting. The geophysics will take place on ground in September.
In June, Dart finalised the farm-in to Great Divide Mining’s (ASX:GDM) Coonambula Antimony-Gold Project, earning an initial 15% stake in the six exploration tenements.
The company can increase that to 51% by completing 4,000m of drilling and reporting two resource calculations within two years.
The Coonambula antimony-gold mineralisation is interpreted to be similar to the style represented at Larvotto Resources’ (ASX:LRV) Hillgrove Antimony-Gold Project, which is also hosted within the New England Orogen but on the New South Wales side of the border.
Early to antimony game
In early 2021, the company mapped out its exploration strategy, stating that besides gold it also had a focus on strategic minerals including antimony.
“We’ve always taken an interest in it and reported it. So we’re not new to antimony,” Chirnside explains.
Dart’s early exposure to antimony was via its Tallandoon and Sandy Creek gold and antimony projects in northeast Victoria.
Over 80 historical hard rock gold workings were recorded at Sandy Creek and a further 94 gold, three antimony and 19 tin workings were recorded at Tallandoon.
Tallandoon historically produced 100,000 ounces of gold and had a 3km gold-antimony trend that also yielded 33.5 tonnes of antimony. Limited recent grab sampling returned up to 6.48% antimony.
Meanwhile, of Dart’s flagship projects, Rushworth in central Victoria sits around 45km east of the Fosterville Gold Mine and was the site of past high-grade gold production. Rushworth borders Australia’s only current producing antimony mine, Costerfield, which is owned by Mandalay Resources (TSX:MND) and produced 1,282 tonnes in 2024.
Dart has identified 14km of historical gold workings at Rushworth and also submitted an application over an area adjoining in the west that has “real antimony potential” in the northern extension of the Costerfield-Redcastle gold-antimony zone under the Murray Basin cover, according to Chirnside.
The application is expected to be granted this year, Chirnside says. “Recent success by Catalyst Metals (ASX:CYL) and others following the Bendigo zone under Murray Basin cover gives us good reason to test under cover for the extension of Costerfield-Redcastle, which as a result of the cover has had no modern exploration.”
Overlooked antimony potential
The Coonambula project is located 130km from Dart’s Triumph Gold Project, which the company discovered had a previously overlooked past producing antimony mine.
Chirnside says it was a bit of good luck for Dart, with the previous owners not having really looked at it.
“The old antimony mine is on the Queensland geology maps, but there’s no information. We understand the workings were significant, and there’s one or two historical references in newspapers indicating that,” he says.
The Triumph project has an existing inferred resource of 150,000 ounces of gold @ 2.17g/t, with over 85% of the resource within 100m of surface.
“We’ve only exploited about 20% of the known strike but some of our recent drilling is pointing to significant additional zones of mineralisation and high-grade depth potential,” Chirnside explains.
“We’ve got two corridors that we’re drilling and exploring and potentially a third corridor.”
Chirnside says Triumph has parallels to the multi-million-ounce Ravenswood mine, which is Queensland’s largest gold mine.
“It’s basically identical host rock, mineralisation style and alteration minerals. We think that there’s good potential for a million-ounce plus at Triumph,” he says. Dart will be announcing an exploration target at Triumph this quarter and Chirnside expects it to showcase the significant potential.
Recently, Dart reported the highest-grade gold intercepts to date from Triumph of 0.3m @ 114g/t gold and 276g/t silver from 171.3m, within 4.4m @ 8.99g/t gold and 28.09g/t silver. In the same hole, another zone returned 3.1m @ 7.98g/t gold and 30.62g/t silver. The results were from the drilling of a down plunge extension at depth to the south of the Big Hans prospect and Dart believes there is potential for a larger intrusion related gold system at depth.
The company has its own diamond drilling rigs, which allows the explorer to drill at about a third of what it would cost to hire a contractor, drill for longer and work to its own schedule.
“We drill a lot more metres than most exploration companies,” Chirnside says.
“If you don’t drill, you’ve got no chance of discovery. We’re not in this game for the lifestyle; we’re in this game to make a discovery.”
Write to Angela East at Mining.com.au
Images: Mining.com.au & Dart Mining
