Stillwater Critical Montana rhodium assays: resource and PEA lens for mine planners
Reviewed by Tom Sullivan

First reported on MINING.com
30 Second Briefing
Stillwater Critical Minerals is advancing its Stillwater West project in Montana with new rhodium assays from eight holes in a 3,472-metre 2025 drill campaign at Chrome Mountain and Iron Mountain feeding an updated resource estimate due next month. The current 2023 inferred resource stands at 255 million tonnes at 0.2% nickel-equivalent cut-off, containing 1.64 billion lb nickel-copper-cobalt, 3.81 million oz palladium-platinum-rhodium-gold, 115,000 oz rhodium and 2.3 billion lb chromium in a Platreef-style, bulk-tonnage setting. Backed by Glencore’s 15% stake and more than 40,000 metres of drilling support, the company is funded for its largest drill programme yet and planning a first PEA later this year.
Technical Brief
- Narrow rhodium-bearing intervals at Chrome Mountain include 1.22 m @ 0.167 g/t Rh from 358 m.
- A second Chrome Mountain interval cut 1.22 m @ 0.107 g/t Rh from 388 m downhole.
- At Iron Mountain, hole IM2025-01 intersected 1.22 m @ 0.148 g/t Rh from 272 m depth.
- Eight rhodium-assayed holes (3,472 m total) targeted Chrome Mountain plus CZ and HGR zones at Iron Mountain.
- CZ and Central deposits already coalesce in surface projection, with HGR only ~700 m distant.
Our Take
The proximity of Stillwater West to Sibanye-Stillwater’s operating Stillwater and East Boulder mines and the Columbus smelter-refinery complex (about 60 km away) suggests any future development could leverage existing PGM processing infrastructure, potentially lowering capex and permitting risk compared with a greenfield build in a new jurisdiction.
Rhodium intercepts at Chrome Mountain and Iron Mountain, although narrow, are notable because most PGM-tagged items in our coverage focus on South African Bushveld operations like Mogalakwena and Platreef, signalling that Montana could emerge as one of the few non-African rhodium contributors if continuity and grades hold up in further drilling.
Prepared by collating external sources, AI-assisted tools, and Geomechanics.io’s proprietary mining database, then reviewed for technical accuracy & edited by our geotechnical team.
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