Larvotto Resources has discovered tungsten lurking in its already economic Hillgrove gold and antimony project in NSW, setting the scene for another payable by-product from the project that is already showing big numbers based on gold and antimony alone. Larvotto has delivered an initial mineral resource estimate for tungsten of 8.77 million tonnes at 0.05% tungsten trioxide at the project for 4774 contained tonnes of product.
The bulk of the new tungsten resource exists in Larvotto’s Clarks Gully and Brackins Spur mineral horizons that are about 6kms apart.
Clarks Gully in the far north of the project contains an estimated 647,000 tonne resource at 0.05% tungsten trioxide for 327 contained tonnes of product.
About 6kms to the south Bracken Spur is also shaping up as a solid tungsten contributor with 2.1Mt assaying 0.16% tungsten trioxide for 3465 tonnes of product.
Notably the tungsten mineralisation is associated with the gold and antimony resource at Hillgrove and could potentially be mined at the same time, providing some economies of scale.
Tungsten ore minerals – predominantly scheelite - have been mined previously at Hillgrove in association with gold and antimony because the three commodities often share a common host environment in Hillgrove’s steep shears and breccia structures.
Historically, the metal was never a priority because of low prices and was either never, or at best, only rarely assayed during drilling campaigns for either gold or antimony.
Larvotto Resources managing director Ron Heeks said: “While Hillgrove has been historically known for its wealth of high-grade antimony and gold mineralisation, there is an exciting tungsten opportunity that exists at the Project. Now that the DFS is complete, we will assess other opportunities to add further value at Hillgrove, including tailings retreatment for gold, antimony and tungsten as well as tungsten as a mining by-product.”
Most importantly, variable concentrations of scheelite, a key host rock for tungsten, are identifiable in all of the deposits at Hillgrove, including at Clarks Gully, Brackins Spur and at Metz, where seven tungsten related structures/trends have been identified and modelled.
The potential for significant economic tungsten mineralisation has never been fully assessed at Hillgrove, despite it being mined along with other gold and/or antimony feedstock and processed as a by-product in the past.
With no dedicated tungsten recovery plant being installed previously at Hillgrove, it is likely that a lot of tungsten mined at the operation, mostly incidentally, has found its way directly into the 1.4Mt tails dam.
The previous operators of the Hillgrove project began installation of a hydrometallurgical extraction circuit for tungsten but it was never completed.
In January last year, Larvotto undertook auger drilling of the old tailings dam on the site for metallurgical testwork after its review of historic production records showed that a significant amount of gold had found its way to the tails.
Tailings assays revealed an average grade of 1.34g/t gold, along with significant antimony and tungsten. Further metallurgical testwork will evaluate the recovery potential of all three metals from the tails.
While it is difficult to get a firm grasp on the price for the tungsten, with considerable fluctuation between metal and ore mineral prices between global trading markets, Larvotto is pinning its hopes on a current tungsten price of around US$48,000 per ton (A$74,700), based on a May 14 Shanghai Metals Market price – a number that would make nickel and copper miners blush.
Larvotto considers the tungsten to be a viable by-product to its gold and antimony production at Hillgrove and says the current process plant configuration already has a tungsten gravity extraction plant in place.
While the company included tungsten in its mineral resource modelling for its recent Definitive Feasibility Study for the project, the metal was never contemplated in the DFS, providing a potentially upside question mark for the project.
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By Doug Bright
