Perth-based Chalice Mining has confirmed its Gonneville project will become Australia’s first primary platinum group metals (PGM) mine, after a prefeasibility study (PFS) outlined a 23-year, two-stage openpit operation with strong economics and scope for expansion.

The study, released on Monday, positions Gonneville as a globally competitive critical minerals project producing palladium, nickel, copper, platinum, gold and cobalt.

The initial openpit phase is forecast to generate A$4.7-billion in free cashflow pretax, with a 2.7-year payback on A$820-million in preproduction capital. At spot prices, cumulative free cashflow would lift to A$6.2-billion.

The mine is set to deliver average 220 000 oz/y of 3E metals and rank as Australia’s second-largest nickel mine, diversifying global PGMs supply that is currently concentrated in Russia, South Africa and Zimbabwe.

MD and CEO Alex Dorsch said in a statement that the PFS “highlights our plan to develop a major critical minerals mine which, due to its scale, longevity and location represents a compelling, unique and strategic opportunity in the sector”.

He added that the project “is viable and will generate solid returns, even at bottom of the cycle prices", noting that the simplified, staged development and conventional processing route “have underpinned a low-risk and financially strong study".

Gonneville holds a maiden ore reserve of 260-million tonnes and leaves roughly half of the broader resource unmined, providing what the company describes as “exceptional upside” through deeper openpit phases or a large-scale underground operation beyond 2054.

Dorsch said the project’s metals suite positions Chalice to supply sectors spanning transport, defence, electronics and clean-energy manufacturing. “Gonneville will help address [global supply] dominance and provide a secure and reliable supply chain from a new independent producer in the western world,” he said.

Offtake discussions ramp up next year, supported by interest from smelters and strategic partners. Dorsch said Mitsubishi, which had been advising during the PFS, had provided “highly valuable” technical and marketing input.

COO Dan Brearley said the company was “absolutely committed to developing [the project] in a sustainable and responsible manner", with work now turning to a full feasibility study, permitting and further engineering derisking. “We have all the right elements to now build a large project on the outskirts of Perth and we are moving up a gear to deliver it on time and on budget,” he said.

A final investment decision is targeted for the first half of 2028, with Chalice stating it was fully funded to reach that milestone.