Stillwater Critical Minerals More Than Doubles Stillwater West Inferred Mineral Resource and Establishes Maiden Indicated Resource

Stillwater Critical Minerals Corp. (PGE) announced an updated and expanded Mineral Resource estimate (2026 MRE) for its Stillwater West project in Montana, USA. The update establishes the company's first Indicated Mineral Resource and significantly expands the Inferred Resource, positioning Stillwater West as the largest known rhodium deposit in North America and the largest nickel and cobalt deposit in an active US mining district. The resource model incorporates new drilling data, refined geological interpretations, and geophysical surveys, providing a technical foundation for future metallurgical testing and mine planning.

At a 0.20% NiTEq cut-off, the Indicated resource totals 29.4 million tonnes grading 0.38% NiTEq, while the Inferred resource stands at 805.1 million tonnes grading 0.34% NiTEq. The total contained metal for the Indicated and Inferred categories combined includes:

• Nickel: 3.01 billion pounds (Blbs)
• Copper: 1.52 billion pounds (Blbs)
• Cobalt: 283 million pounds (Mlbs)
• Platinum: 2.28 million ounces (Moz)
• Palladium: 3.97 Moz
• Gold: 864 thousand ounces (Koz)
• Rhodium: 310 Koz

The release also presents resource estimates at 0.35% and 0.50% NiTEq cut-offs to represent higher-grade zones. Additionally, the Inferred chromium resource was expanded to 6.6 billion pounds, though chromium is not included in the NiTEq calculations or economic assumptions.

The geological model covers four zones across the central 10-kilometer project area, with previously separate CZ and Central deposits at Iron Mountain now combined. The model incorporates 14 new drill holes (5,781 meters) from 2023 and 2025 campaigns plus verified historical data. Qualified Persons Timothy O. Kuhl and Dr. Ted Eggleston of Mine Technical Services prepared the estimate.

Technical assumptions for the NiTEq calculation were based on metal prices of Ni $8.00/lb, Cu $4.50/lb, Co $11.00/lb, Pt $1,250/oz, Pd $1,250/oz, Au $3,000/oz, and Rh $6,500/oz, with recoveries set at 80% for Ni, Co, Pt, Pd, Au, and Rh, and 85% for Cu. The pit shell assumed open pit mining with a mining cost of $2.50/t, processing cost of $18/t, and a 50° pit slope.

Michael Rowley, President and CEO, stated: "This updated Mineral Resource estimate marks an important step forward for Stillwater West. Beyond the substantial increase in the estimated tonnage and contained metal, the establishment of our first Indicated Mineral Resource and the continued refinement of our geological model significantly enhance our understanding of this large and evolving mineral system."

Dr. Danie Grobler, Vice-President Exploration, added: "The 2026 resource estimate reflects the integration of new drill results, historical data, structural interpretation, and geophysical information into an increasingly robust geological model. That work has significantly improved our understanding of the continuity and geometry of mineralization across the district, supporting the classification of the Company's first Indicated Mineral Resource..."

The project is adjacent to Sibanye-Stillwater’s operating PGE mines in Montana. The company also holds interests in other projects including Drayton-Black Lake (49% interest), Kluane PGE-Ni-Cu-Co, Duke Island, and Yankee-Dundee. Stillwater Critical Minerals Corp. will participate in several upcoming events, including the Commodities Global Expo in Phoenix, AZ (Sept 18-20, 2026), the Precious Metals Summit in Beaver Creek, CO (Sept 22-25, 2026), Better in Our Backyard in Minneapolis, MN (Sept 29 - Oct 2, 2026), the AEMA Annual Meeting in Sparks, NV (Dec 6-11, 2026), and the Montana Mining Association Winter Meeting in Billings, MT (Dec 8-9, 2026).