Resolution Minerals Ltd (ASX:RML, OTCQB:RLMLF, FRA:NC3) has outlined growing scale potential at its Antimony Ridge project in Idaho, with new 3D modelling pointing to a large, open-ended system of high-grade antimony-silver veins.
The modelling integrates historical mining data, mapping and sampling to define more than 100 high-grade stibnite veins organised into around 30 discrete vein swarms, extending across a broad 1,000-by-700-metre footprint.
Antimony Ridge – High grade antimony veins and mineralisation with assays, modelled as 30 discrete mineralised vein swarms, fault breccias and stockworks, within past open pits and trenches. Veins and vein swarms are surrounded by a lower grade antimony halo of veinlets and stockwork shown in a coloured antimony-in-soil geochemical anomaly map with averaged assays. Veins, assays and soil geochemistry are draped over a 3-D shaded image. Results extend over a large area 1000m x 700m and 250m vertically.
The results build on recent momentum at the Horse Heaven project, following the project’s inclusion in the US government’s FAST-41 permitting initiative earlier this week — a move expected to accelerate approvals for drilling and bulk sampling.
Large, high-grade system taking shape
The new 3D interpretation highlights a structurally controlled, “en echelon” vein system — where multiple veins are arranged in a staggered, step-like pattern along the same structural trend — with mineralisation extending vertically over roughly 250 metres and remaining open in all directions.
Antimony Ridge – High grade antimony veins within past open pits and trenches with results of rockchip draped over a shaded topographic map sampling
“Such is the consistency of the vein frequency, and the vein swarms, that there is a high probability that future work will uncover more veins and extend the length and width of the system,” Resolution CEO of US operations Craig Lindsay said.
Historical mining and recent sampling continue to reinforce the grade profile. Bulk rock samples from past workings have returned antimony grades ranging from 31.7% to 48.7% Sb, alongside silver grades averaging 430 g/t and gold credits.
Those high-grade veins sit within a broader halo of lower-grade mineralisation — typically between 0.5% and 2% antimony — pointing to a large mineralised system rather than isolated structures.
“The modelling has revealed significant size potential, which demonstrates the strategic importance of Antimony Ridge as a potential source of US domestic antimony supply,” Lindsay said.
Strategic location and historical context
Antimony Ridge sits within Resolution’s broader Horse Heaven antimony-tungsten-gold-silver project in Idaho, adjacent to Perpetua Resources’ Stibnite project — one of the most advanced antimony developments in the United States.
Antimony Ridge – As part of Resolution’s larger Horse Heaven Antimony-Tungsten-Gold-Silver Project.
The district has a long history of production, with Antimony Ridge itself mined during World War I, World War II and the Korean War. At its peak, the broader region is estimated to have supplied more than 90% of US antimony, underscoring its strategic importance.
That historical footprint also provides a head start for modern exploration, with existing pits, trenches and access already exposing mineralised zones and reducing early-stage development barriers.
Antimony Ridge – Past open pits and trenches from WWI & II and Korean War, with access roads, in 3D satellite image looking NE.
FAST-41 status strengthens development pathway
The modelling update follows Resolution’s recent inclusion in the US FAST-41 Transparency Coverage program, designed to streamline permitting for critical infrastructure and resource projects.
That designation is expected to support approvals for up to 250 drill holes and large-scale bulk sampling — key steps in advancing Antimony Ridge towards development.
The project’s positioning as a potential domestic source of antimony — a critical mineral used in defence, energy storage and industrial applications — has been central to its selection.
Next steps: Drilling, metallurgy and bulk sampling
Resolution is now preparing to advance the project on multiple fronts.
Near-term work will focus on metallurgical test results from a 100-kilogram bulk sample of high-grade stibnite, with studies under way across pyro- and hydrometallurgical processing pathways. The company is targeting production of antimony trioxide for potential qualification with US end users.
At the same time, permitting under FAST-41 is expected to unlock a large-scale drilling program, alongside bulk sampling to better define the geometry and continuity of the vein system.
Beyond Antimony Ridge, exploration is also ramping up across the broader Horse Heaven project, including a planned Phase 2 drilling campaign at the Golden Gate prospect in May.
Expanding US critical minerals platform
The latest modelling reinforces Antimony Ridge as a cornerstone asset within Resolution’s US-focused critical minerals strategy, which also includes tungsten stockpiles and gold exploration across the Horse Heaven district.
The company is also advancing tungsten development pathways alongside follow-up drilling at nearby targets, positioning the broader project as a multi-commodity growth platform.
With high-grade mineralisation confirmed at surface, a large-scale system taking shape and permitting momentum building, Resolution is now moving to test the full extent of what could become a significant domestic antimony supply source.