Altar's $2B Potential Clouded by Rio Tinto Venture's Sudden Exit

VANCOUVER, BC – November 24, 2025 – Aldebaran Resources Inc. delivered a conflicting message to the market today, simultaneously celebrating a highly positive economic forecast for its flagship Altar copper-gold project in Argentina while also announcing the termination of a pivotal partnership with a Rio Tinto-backed venture. The news sent the company's stock tumbling, as investors weighed the project's impressive long-term value against the immediate uncertainty created by the departure of a major industry partner.

On one hand, the company filed a Preliminary Economic Assessment (PEA) for the Altar project, outlining a financially robust, large-scale mining operation. The study projects a post-tax Net Present Value (NPV) of US$2 billion at an 8% discount rate and a strong Internal Rate of Return (IRR) of 20.5%. These figures paint the picture of a world-class asset capable of delivering significant copper, gold, and silver production for decades.

On the other hand, this optimistic outlook was immediately tempered by the concurrent announcement that Nuton Holdings Ltd., a Rio Tinto venture focused on novel leaching technologies, was terminating its option to acquire a 20% interest in the project. The market reaction was swift and decisive: Aldebaran’s shares (TSX-V: ALDE) plunged over 15% in trading, indicating that the loss of a heavyweight partner overshadowed the project's strong paper economics.

A Tale of Two Signals

The dual announcements have created a classic conflict for investors. The PEA, prepared by consulting firm SRK, validates Altar as a top-tier development project. The base case envisions a conventional concentrator with a long mine life, attractive cash costs, and a manageable initial capital expenditure of US$1.59 billion relative to its massive scale.

“The PEA demonstrated that the base case concentrator scenario for Altar is a long-life project delivering significant copper, gold, and silver production at attractive cash costs while minimizing upfront capital,” commented John Black, CEO of Aldebaran, in the company's press release. He emphasized the project's attractiveness and its importance for Argentina's future.

However, the withdrawal of Nuton introduces a significant element of doubt. Major mining companies like Rio Tinto conduct extensive due diligence, and their participation is often seen as a powerful de-risking event and a stamp of technical approval. While Aldebaran retains its 80% interest in the project, the loss of a partner with deep pockets and technical expertise, particularly Nuton's proprietary bio-leaching technology, raises questions about the project's future development path and financing strategy. The sharp decline in Aldebaran's stock price, which had reached an all-time high in anticipation of the PEA results, suggests the market is pricing in a higher risk profile and a longer, more arduous road to production.

Deconstructing the Exit: A Strategic Pivot

Aldebaran was quick to frame Nuton’s decision as a strategic realignment rather than a vote of no-confidence in the Altar project itself. According to the company, Nuton is “shifting priorities to focus on later-stage projects that could potentially deliver nearer-term production.”

This explanation is substantiated by external evidence. On the same day, Nuton announced it was exercising its option to advance to Stage 3 of its agreement for the Yerington Copper Project in Nevada. This move involves funding a Definitive Feasibility Study (DFS)—a much more advanced stage of study than Altar's PEA—signaling a clear corporate focus on assets closer to a construction decision. This action lends credibility to the narrative that Nuton's withdrawal was part of a broader portfolio management decision at Rio Tinto, rather than a reaction to a specific flaw discovered at Altar.

Despite the termination of the equity option, the door remains open for a future technology licensing agreement. This would allow Aldebaran to potentially still utilize Nuton’s innovative bio-leaching technology to process lower-grade material, but it falls far short of the comprehensive financial and technical partnership that an equity stake would have entailed. Without Rio Tinto as a direct partner, the burden of advancing and funding the multi-billion-dollar project falls more heavily on Aldebaran and its remaining joint venture partner, Sibanye-Stillwater.

Altar in a Competitive Copper Landscape

Placed in the context of its peers, Altar's PEA metrics hold up well but also highlight the immense challenges ahead. The project is situated in Argentina's San Juan province, part of a cluster of world-class porphyry copper deposits. Its most direct comparable, McEwen Copper’s nearby Los Azules project, recently published a Feasibility Study showing a US$2.9 billion NPV and a 19.8% IRR. However, its estimated initial capital cost ballooned to US$3.17 billion, nearly double Altar's current PEA estimate—a cautionary tale of how costs can escalate as projects move toward reality.

Altar’s US$1.59 billion initial capital estimate is a significant hurdle for a junior company to finance alone. The loss of a potential funding partner like Rio Tinto makes this challenge steeper. While the project's economics are strong, securing the necessary capital in a competitive market will be a defining test for Aldebaran's management team.

Looking ahead, Aldebaran plans to advance the project towards a Pre-Feasibility Study (PFS) with its existing 20% partner, Sibanye-Stillwater. This next phase will be critical in refining the engineering, updating cost estimates, and further de-risking the project in the eyes of the market. As Aldebaran moves forward, it must prove that the intrinsic value of the Altar deposit is compelling enough to attract new partners and capital, independent of the major that just walked away.