Castile Posts $1.07B NPV Study After Bismuth Addition Unlocks $600M Revenue Stream
Key Takeaways
- The Castile Resources Rover 1 Scoping Study models a pre-tax NPV₈ of $1,067.5M and a 59% pre-tax IRR, with total revenue of A$4.78 billion across an 11-year initial mine life.
- Bismuth has been included in the financial model for the first time, adding approximately $600M in revenue and establishing Rover 1 as a five-metal project producing gold, copper, bismuth, cobalt, and high-grade magnetite.
- Pre-production CAPEX is just $170.5M for Stage One, with the $274.9M Stage Two Darwin refinery funded entirely from operating cashflows — keeping the upfront funding ask unusually low relative to project scale.
- Capital payback is estimated at approximately two years after production commences, and the upside case — using higher commodity prices — lifts NPV to $1.477 billion and IRR to 76.9%.
- The BFS is due later in 2026, but the Study carries a material caveat: approximately 30% of the resource base is Inferred, no ore reserves have been estimated, and no formal financing agreements are in place.
Castile’s five-metal Rover 1 study delivers $1.07B NPV and $4.78B revenue
In its August 2026 updated Scoping Study, Castile Resources (ASX: CST) outlined the economics of its 100%-owned Rover 1 IOCG Project, southwest of Tennant Creek, NT. The Study models a pre-tax NPV₈ of $1,067.5M, a pre-tax IRR of 59%, total revenue of A$4.78 billion, and an 11-year initial mine life, with pre-production CAPEX of $170.5M. The company presented a two-stage development pathway: an underground mine and 750,000tpa processing plant at site (Stage One), followed by construction of a refining facility at the Middle Arm Sustainable Development Precinct in Darwin using Stage One cashflows (Stage Two). This is the first time Castile has included bismuth in the model — a modelling first for the company — adding approximately $600M in revenue and establishing the project’s five-metal revenue base.
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Rover 1 study headline numbers
The Study presented base-case economics driven by low upfront capital and strong metal-price leverage. The base-case assumes A$7,143/oz gold, A$23,621/t copper, A$50/lb bismuth, A$85,714/t cobalt and A$300/t magnetite, with an 8% discount rate applied. The upside case uses higher commodity prices (gold US$7,667/oz, copper US$7.37/lb, bismuth US$42.18/lb, cobalt US$88,083/t, magnetite US$230/t at an exchange rate of US$0.77:A$1) rather than a different mine plan. Capital payback is approximately two years after production commences, reflecting strong capital efficiency.
| Metric | Units | Scoping Study Outcome | Upside Case Outcome |
|---|---|---|---|
| Total Revenue | A$M | $4,784.0M | $5,479.6M |
| Project Cash Flow | A$M | $1,946.0M | $2,598.1M |
| NPV₈% (pre-tax) | A$M | $1,067.5M | $1,477.0M |
| NPV₈% (post-tax) | A$M | $677.6M | $948.1M |
| IRR (pre-tax) | % | 59.0% | 76.9% |
| IRR (post-tax) | % | 44.6% | 58.4% |
| Pre-Production CAPEX | A$M | $170.5M | $170.5M |
The low CAPEX relative to NPV signals strong capital efficiency. The project generates $1.95 billion pre-tax cashflow at the base case, with minimal sustaining CAPEX in early years outside of mine development and the Stage Two refinery build.
The bismuth boost: how a fifth metal added $600M
Gold and copper anchor the valuation — 269,000oz gold and 72,200t copper over the initial mine life — with bismuth, cobalt and high-grade magnetite providing additional revenue streams. The Study is the first time Castile has modelled bismuth revenue at Rover 1.
Mark Hepburn, Executive Chair & MD
“The results of the Rover 1 Scoping Study show the extraordinary financial impact of having five revenue streams from one mine with the recent addition of bismuth. The added time and work to get the bismuth into this study has paid off with an additional $600M in revenue generation.”
The five revenue streams (life-of-mine payable production):
- Gold — 269,000oz
- Copper — 72,200t
- Bismuth — 5,400t
- Cobalt — 2,700t
- High-grade magnetite (96.4% Fe₃O₄) — 1,101,500t
Bismuth extraction testing is not yet complete to Pre-Feasibility or Bankable Feasibility Study level. Final testing will be completed and included in the BFS due later in 2026.
What is an IOCG deposit — and why five revenue streams matter
Iron Oxide Copper Gold (IOCG) deposits are polymetallic systems where copper and gold sit within a magnetite-rich alteration halo, alongside by-products like cobalt and bismuth. Rover 1’s five products diversify commodity price exposure and smooth cashflow — if one metal weakens, the others can compensate.
The critical minerals angle matters to investors. Bismuth and cobalt are both subject to supply constraints: approximately 80% of global bismuth supply is Chinese, and China imposed export licensing requirements on bismuth in February 2025. Cobalt faces similar concentration risk, with the Democratic Republic of Congo (DRC) controlling 70–80% of global mined cobalt and having imposed export quotas in October 2025. Rover 1’s Australian production provides exposure to critical minerals with constrained, geopolitically concentrated markets — and potentially commands a provenance premium versus Chinese or DRC-origin material.
Staged development plan
The Study models a two-stage build to reduce upfront capital intensity and add funding flexibility. Stage One builds an underground mine and modern 750,000tpa processing plant at the Rover 1 site producing concentrates: gold, copper, bismuth, cobalt and magnetite. Stage Two adds a refining facility at the Middle Arm Sustainable Development Precinct (MASDP) in Darwin, funded using Stage One cashflows, to produce final products for direct sale.
Final products:
- Gold doré
- 99% copper cathode
- Bismuth concentrate
- Cobalt hydroxide
- High-purity magnetite concentrate (96.4% Fe₃O₄)
The staged approach reduces upfront capital — the $170.5M pre-production CAPEX covers Stage One only. The Stage Two refinery (estimated $274.9M sustaining CAPEX) is built from operating cashflow, not upfront equity or debt. This structure materially changes the funding ask and improves the company’s flexibility to optimise financing terms.
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Funding position and path to the BFS
Castile reported a cash position of $9.37M as at 30 June 2026 — described as sufficient to complete BFS requirements. The BFS is due later in 2026, and this Scoping Study serves as its foundation. The company has not yet entered formal funding negotiations, but intends to begin discussions on the strength of the Study outcomes. Funding strategies to be explored include traditional debt and equity, plus potential metal prepayments, metal streams, offtake agreements or joint ventures.
Mark Hepburn, Executive Chair & MD
“The staged approach to the development adds flexibility to our funding strategy and Castile will now begin formal funding negotiations on the strength of this Scoping Study that will be the foundation of the Bankable Feasibility Study due in 2026.”
Indicative development schedule:
- Bankable Feasibility Study — 2026
- Permitting and Approvals — 2027–2028
- Construction Phase — 2027–2029
The Study is preliminary and based partly on approximately 30% Inferred Mineral Resources. No ore reserves have been estimated, and no formal financing agreements are in place. There is no certainty funding will be available when required.
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