Key Highlights

  • The updated Rover 1 Scoping Study shows a pre-tax NPV8 of A$1,067.5 million and a pre-tax IRR of 59.0% on A$170.5 million of pre-production capital.
  • Total revenue is A$4.78 billion over an initial 11 years, with bismuth contributing about A$595 million, or 12%.
  • Drillhole 26P38D01 at Pathfinder 38 reached 574 metres before being suspended, with downhole electromagnetic surveys planned for early November 2026.
  • Cash stood at about A$7.46 million at 30 September 2026, after A$1,593k of exploration and study spending.

Castile Resources Limited (ASX:CST) used its September 2026 quarterly report to set out an updated Rover 1 Scoping Study that adds bismuth to a production profile that already included gold, copper, cobalt and magnetite. The study returns a pre-tax NPV8 of A$1,067.5 million and a pre-tax IRR of 59.0% for an underground mine near Tennant Creek in the Northern Territory. Alongside the study, the company progressed pilot plant testing, suspended a deep hole at Pathfinder 38 and reported cash of about A$7.46 million.

Rover 1 Scoping Study Economics

Released on 28 August 2026, the base case assumes a copper price of US$7.50/lb, gold at US$5,000/oz, bismuth at US$35.00/lb, cobalt at US$60,000/t and magnetite at US$210/t, with an exchange rate of 0.70. On that basis the post-tax NPV8 is A$677.6 million and the post-tax IRR 44.6%. The upside case, using life-of-project average prices and an exchange rate of 0.77, lifts pre-tax NPV8 to A$1,477.0 million and the pre-tax IRR to 76.9%.

Total revenue is A$4.78 billion over an initial 11-year life, averaging A$477.2 million a year, against project operating costs of A$1,938.0 million and project cash flow of A$1,946.1 million. Gold and copper generate 76% of revenue, and the remaining A$1.16 billion comes from bismuth, magnetite and cobalt. Over the mine life the study covers 7,264,700 tonnes of ore, producing 269,000oz of gold, 72,200t of copper, 5,400t of bismuth, 1,101,500t of magnetite and 2,700t of cobalt, from a processed grade of 1.32g/t gold and 1.05% copper.

Pre-production capital is A$170.5 million including 10% contingency, split between A$98.5 million for the process plant, A$52.0 million for mine infrastructure and A$20.0 million for surface infrastructure. A Darwin refinery costing A$274.9 million would be funded later from Stage 1 cash flow. All-in sustaining cost is A$3,920 per gold-equivalent ounce against a base-case gold price of A$7,143/oz.

Testwork, Approvals and Exploration

Bismuth testwork during the quarter delivered recoveries the company described as above expectations, and Castile is evaluating a bismuth cement product on site, with bench-scale work to start immediately. An independent review of the metallurgical results pointed to additional gold recovery from the gold concentrate, and pressure oxidation tests matched historical outcomes. Paste samples from tailings were received by Quatro Engineering, which supplied capital and operating cost estimates for the bankable feasibility study. On approvals, True North has begun the Social Impact Assessment for the Environmental Impact Statement, and ATC Williams completed preliminary designs for the tailings storage facility.

At Pathfinder 38, drillhole 26P38D01 reached 574 metres before being suspended to assess unexpected banded iron formation and magnetite-bearing metasiltstone and shale. Modelling indicates these units do not account for the magnetic anomaly, so downhole electromagnetic and magnetic surveys are scheduled for early November 2026. Passive seismic sensors were deployed over Rover 7, Rover 27, Pathfinder 2 and Pathfinder 38 and are now operating at Rover 8. At the Warumpi Project, outcrop mapping verification at Huron was completed in August, and an induced polarisation survey is planned over magnetic basement rocks extending 2 km along strike and 600 m wide.

Corporate Activity and Finances

The Rover 1 data room is active with domestic and offshore mining companies and financiers, and production samples have been prepared for prospective customers. Castile presented at the Mining the Territory Conference and is in discussions with governments seeking ex-China bismuth supply. The Northern Territory added bismuth to its critical minerals list in 2026. Cash was about A$7.46 million at 30 September 2026, exploration and study expenditure for the quarter was A$1,593k, and payments to directors and related parties were A$190k. No lost time injuries were reported and no tenements were acquired or disposed of.

Where the Quarter Leaves Castile

Castile finished the quarter with a scoping study that quantifies five products across 11 years, a pilot plant program awaiting bismuth extraction and regrind results, and an exploration drill hole paused at 574 metres. Its balance of A$7.46 million compares with A$1.59 million of quarterly exploration and study spending.