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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