Highlights

  • A laboratory-scale continuous pilot of the full Gonneville process flowsheet has commenced, testing approximately five tonnes of fresh sulphide ore representative of early plant feed.
  • The PGM leach elution process has been simplified from five steps to two, with a nickel-based stripping solution replacing a higher-cost zinc-based solution assumed in the Pre-Feasibility Study.
  • Concentrates produced during the pilot will be provided to international copper and nickel smelters and metals traders that have expressed interest in offtake.
  • The Definitive Feasibility Study is ongoing and remains on track for completion in the second half of calendar year 2027.

Chalice Mining Limited (ASX:CHN) has provided an update on the ongoing Definitive Feasibility Study and execution readiness work at its 100%-owned Gonneville PGM-Nickel-Copper-Cobalt Project in Western Australia. The commencement of a continuous laboratory-scale pilot of the full Gonneville process flowsheet marks an important step in the project's development, described by the company as the final de-risking step required to achieve bankability for the process flowsheet.

The pilot is processing approximately five tonnes of fresh sulphide ore, drilled specifically for the program across ten PQ diamond core holes. The ore is representative of the early plant feed across all eleven identified geo-metallurgical domains within the project's resource. It is being processed through the flotation concentrator and leach circuit using treated wastewater from an Alkimos facility, simulating the real-world conditions anticipated at a future commercial plant.

Process Flowsheet and Pilot Structure

The Gonneville flowsheet comprises an industry-standard comminution circuit followed by two-stage sequential flotation and a precious metal leach circuit. The pilot is designed to run in three distinct phases: an initial flotation stage treating the full five tonnes over approximately one week, a sulphide flotation tails leach stage treating around two tonnes over three weeks commencing in late November, and an oxide-sulphide blend leach stage commencing in January 2027. The pilot is expected to produce three distinct product streams — a copper-PGM-gold smelter concentrate, a nickel-cobalt-PGM-gold smelter concentrate and a PGM doré.

An independent technical engineer appointed by the company's Debt adviser is supervising the pilot plant and assessing all technical aspects of the Definitive Feasibility Study. Initial results from the flotation phase are anticipated in early calendar year 2027, with full results for the leach phase expected in the second quarter of 2027.

Leach Circuit Simplification and Cost Implications

A significant improvement has been made to the leach circuit design ahead of the pilot. Chalice has simplified the PGM leach elution process from five steps to two by switching to a nickel-based stripping solution generated from soluble nickel in the leach liquor itself, in place of a higher-cost zinc-based solution assumed in the Pre-Feasibility Study completed in December 2025. The company considers this change likely to result in meaningful reductions to both Capital and operating costs associated with the leach circuit, while also de-risking the overall process flowsheet.

Engineering work is ongoing to quantify the precise cost reductions relative to Pre-Feasibility Study assumptions. The PGM doré produced in the pilot is expected to be the first of its kind refined in Australia, and offtake discussions with domestic refiners including the Perth Mint have already commenced. Local refining is considered a potential strategic advantage for the project, contributing to Australia's sovereign processing capabilities.

Offtake Interest and Project Scale

Several international copper and nickel smelters and metals traders have expressed interest in offtake for the concentrates expected to be produced at Gonneville. Additionally, tightness in global sulphur Supply has driven new interest in nickel offtake from hydrometallurgical nickel processing facilities in Indonesia. All products from the project are currently uncommitted, and the pilot concentrates will be used to generate product samples for future discussions.

The project is modelled to produce approximately 45,000 tonnes of copper concentrate and around 95,000 tonnes of nickel concentrate per annum over more than 23 years of open-pit operation. The mineral resource extends beyond the limits of the modelled open pit, suggesting potential for expansion or life extension beyond the current modelled parameters. The Definitive Feasibility Study continues across key workstreams including geotechnical, mining, processing, Marketing and infrastructure, with completion targeted for the second half of 2027.

Key Insights

The commencement of the Gonneville full-flowsheet pilot represents a meaningful step in Chalice Mining's path toward project bankability. The simplified leach circuit design is expected to reduce both capital and operating costs relative to the Pre-Feasibility Study, adding further confidence in the economic case. Early interest from international offtake counterparts in both copper and nickel concentrates reflects the market relevance of the project's production profile. With the Definitive Feasibility Study on track for the second half of 2027 and an independent technical engineer overseeing the pilot, Gonneville's development program remains well-structured. The local refining option for PGM doré adds a strategic dimension to the project beyond pure economics.