Horse Heaven: a Credible Bet on US Critical Minerals Security

China’s export restrictions on tungsten and antimony stopped being a policy talking point sometime around the start of 2026. They became a procurement problem. Defence contractors, battery manufacturers, and semiconductor suppliers are now competing for supply from a market where the dominant producer has deliberately tightened the valve, and the gap between what Washington says it wants and what domestic geology can actually deliver has rarely looked wider.

That gap is where Resolution Minerals (ASX: RML, OTCQB: RLMLF) has positioned its Horse Heaven Project in Idaho. Horse Heaven is not a gold explorer that bolted “critical minerals” onto its pitch deck. It sits in the historic Stibnite mining district, directly neighbouring Perpetua Resources’ deposit (which Perpetua has described as the largest known antimony project in the United States), with confirmed high-grade tungsten production history and a processing mill already acquired. Craig Lindsay, CEO of US Operations at Resolution Minerals, has publicly identified downstream processing capability, not ore supply, as the most difficult constraint in domestic critical mineral development. That framing shapes everything about how this project is structured.

What follows is not a company profile. It is a structured investor assessment of whether Horse Heaven represents a credible strategic position in the US critical minerals thematic, where the execution risks sit, and how the three value levers (antimony, tungsten, gold) interact to define the risk-return picture.

Why tungsten and antimony are not interchangeable with other critical minerals

The US critical minerals list contains dozens of entries. Most of them carry strategic importance in the abstract. Tungsten and antimony carry it in the specific: both metals have non-substitutable defence and industrial applications, and both face supply concentration problems that no amount of recycling or material science can solve in the near term.

Tungsten’s applications include:

• Hard-metal cutting tools used across manufacturing
• High-temperature components for aerospace and energy systems
• Armour-piercing munitions

Antimony’s applications include:

• Flame retardants for defence and commercial use
• Lead-acid batteries and emerging grid-scale energy storage chemistries
• Semiconductor manufacturing
• Specialised defence systems including tracer and night-vision technology

Both metals sit on the US critical minerals list. Both are overwhelmingly sourced from China. And in 2026, China’s export restrictions on relevant critical minerals moved from threatened to implemented, creating a live supply-chain catalyst that distinguishes tungsten and antimony from metals where the supply risk remains theoretical.

The constraint, however, is not simply about finding ore in the ground. Lindsay’s public observation is worth sitting with:

Processing capability represents the most challenging aspect of domestic critical mineral development. The problem goes beyond mine supply alone.

The United States has mines. What it lacks is the downstream capacity to turn mined material into products that defence contractors and battery manufacturers can actually use. That processing deficit is the structural bottleneck, and it is where the Horse Heaven thesis either gains credibility or falls apart.

What the Horse Heaven geology actually claims, and what it still needs to prove

Horse Heaven covers approximately 59 km² (roughly 14,580 acres) in Idaho’s Stibnite mining district, 100% owned by Resolution Minerals since its 2025 acquisition. The project hosts three distinct mineralisation zones, each at a different stage of evidential support. Understanding where each sits on the confidence spectrum is the first step to evaluating the investment case.

No modern JORC or NI 43-101 compliant resource has been defined for tungsten or antimony. A JORC resource is a mineral concentration classified by confidence level (Inferred, Indicated, or Measured) with reasonable prospects for eventual economic extraction. Until one exists for the critical minerals at Horse Heaven, the investment case rests on historic data and surface evidence, not on independently verified estimates.

The tungsten case: historic grade and a processing asset already in hand

The Golden Gate trend hosts a historic underground tungsten mine that reportedly produced ore grading approximately 1.85% WO₃, a figure that is high relative to many modern tungsten operations globally. Modern stockpile sampling has confirmed that grade with low impurities, and the dominant tungsten mineral is scheelite, a characteristic that is metallurgically favourable because scheelite responds better to standard processing methods than its alternative, wolframite.

Resolution has acquired approximately 2,000 tonnes of tungsten ore stockpiles at the Johnson Creek mill site, with internal estimates suggesting potential upside. A dedicated tungsten drill programme is advancing from mid-2026, informed by metallurgical testwork and historical data review. The historic production record, including wartime supply to the US government during World War I, World War II, and the Korean War, gives the tungsten case a foundation that goes beyond theoretical geology.

The antimony case: a geological analogue with surface credentials and an open drill question

Antimony Ridge sits in the same district and structural framework as Perpetua Resources’ large gold-antimony system on the immediate eastern boundary. Surface rock-chip samples returning up to approximately 48.7-50% antimony are exceptionally high-grade results, and the associated silver and gold credits add potential economic upside.

The analogue to Perpetua is geologically compelling. But analogues do not guarantee equivalent deposit scale. What converts the Antimony Ridge thesis from a promising surface story to a bankable resource is a drilling pipeline on the order of 100-plus holes over time. Resolution’s 2026 programme has reached 33-plus holes for approximately 9,700 m drilled, with up to 45 holes and approximately 13,700 m targeted under the expanded scope. That work will determine whether the high-grade surface sampling translates into continuous mineralisation at depth.

The processing gap is where Resolution is making a differentiated bet

Most junior explorers in the critical minerals space assume that processing capacity will materialise once the resource is defined. Resolution has inverted that sequence. In 2026, the company acquired the historic Johnson Creek Tungsten and Antimony Mill, located adjacent to Horse Heaven on approximately 25 acres of private land.

That acquisition matters most not as a standalone asset but as evidence that Resolution is structuring Horse Heaven as a complete domestic supply chain: mine, mill, and saleable product within a single corporate framework. For an investor evaluating the cohort of junior critical minerals explorers, this is the distinguishing feature. Lindsay’s public framing is that processing capability is the hardest problem; Resolution’s response is to acquire the processing infrastructure before the resource is formally defined.

Metallurgical testwork is underway with Kingston Process Metallurgy among the partners involved. Stockpile sampling has confirmed 1.85% WO₃ grades with low impurities and scheelite-dominant mineralogy. The sequential milestones required to move Johnson Creek from acquired asset to operating facility are:

1. Completion of metallurgical testwork on existing stockpiles and newly drilled ore
2. Permitting for mill refurbishment and operation
3. Capital allocation for refurbishment and commissioning
4. Commissioning of processing circuits
5. First saleable tungsten or antimony product

Resolution disclosed an unsolicited US$225 million non-binding proposal for Horse Heaven, a signal that external industrial or strategic counterparties are already valuing the asset’s processing potential, not just its geology.

The execution bar is high. Constructing or refurbishing processing capacity for speciality metals in the US requires substantial capital, permitting work, technical capability, and a stable policy environment. For a junior explorer, managing simultaneous drilling, mill refurbishment, metallurgical testwork, and permitting represents a significant funding burden. The processing strategy either compresses the timeline to production or concentrates capital and execution risk at an early stage. An investor should hold both possibilities simultaneously.

Reading the policy environment without overstating it

What the policy window enables for Horse Heaven specifically

The 2026 policy environment for domestic critical minerals is as supportive as it has been in decades. Horse Heaven sits squarely within it.

Active policy supports:

• FAST-41 designation secured for key project components, providing a streamlined federal permitting pathway that reduces the bureaucratic timeline relative to standard processes
• China’s export restrictions on tungsten and antimony, providing live commercial urgency for domestic alternatives
• Tungsten and antimony prices elevated in 2026 amid supply constraints and demand from defence, clean energy, and technology sectors
• Idaho’s well-established mining heritage spanning gold, silver, base metals, and critical metals, providing a supportive state-level backdrop
• The project sits in the Boise National Forest with US Forest Service permitting oversight, a federal land-use framework that is well-understood if not fast

What investors should watch for policy to become commercial

Policy tailwinds are real. They are also impermanent. Administrations change, tariff regimes shift, and the durability of any single procurement preference or funding mechanism over a 15-20 year project life is not something a junior explorer can assume.

Policy risk factors:

• No guarantee that current FAST-41 or critical minerals procurement preferences persist through successive administrations
• Global tungsten and antimony pricing is sensitive to Chinese supply behaviour, which could reverse if trade dynamics shift
• Federal land-use permitting, even with streamlining, remains a multi-year process with inherent regulatory uncertainty

The milestone events that signal policy tailwinds converting to commercial traction are specific and observable: signed offtake commitments with defence or industrial counterparties, defence-linked funding announcements, formal processing permits for Johnson Creek, or a follow-on strategic proposal that advances beyond non-binding interest.

The US$225 million unsolicited proposal is the most tangible evidence of commercial interest to date, but it remains non-binding. For an investor, the most useful frame is to treat policy support as a window that accelerates certain milestones, and then ask whether Resolution can reach those milestones within the window.

Where Horse Heaven sits in a portfolio anchored to the critical minerals thesis

Horse Heaven is an early-stage optionality play, not a near-term cash-flow story. That distinction matters for portfolio construction. The type of investor for whom this position makes sense is one who is already allocated to the US critical minerals thematic and wants leveraged exposure to tungsten and antimony specifically, with the patience for a multi-year resource definition and processing validation timeline.

The three value levers, ranked by proximity to commercial validation rather than geological grade:

• Tungsten: Historically productive, metallurgically confirmed, with processing infrastructure already in hand. Nearest to a defined pathway.
• Gold: Active 2026 drill programme with maiden resource targeted. Provides scale and optionality.
• Antimony: Geologically compelling surface results and district-scale potential, but requires drill-defined resources before the commercial case can be underwritten.

The analytical question for a portfolio allocation decision is not whether the geology is interesting. It is at what stage of de-risking Horse Heaven warrants a position, and which specific events should trigger that reassessment.

How to position optionality at the geology-policy intersection

Horse Heaven is a leveraged optionality position on US critical minerals security. The geological and processing foundation is credible but still to be proven at a compliant resource level. The right way to hold this thesis is to separate the variables Resolution’s management can control from those they cannot.

Controllable (management execution):

• Drill bit delivery: converting surface results and historic data into compliant resources
• Processing permitting and Johnson Creek mill refurbishment
• Capital management across simultaneous programmes
• Metallurgical testwork and processing route demonstration

Uncontrollable (macro environment):

• Chinese supply behaviour and global tungsten/antimony pricing
• US policy durability across administration changes
• Defence procurement priorities and funding mechanism availability
• Perpetua Resources’ development timeline as a district catalyst

The processing differentiator (Johnson Creek acquisition) is the most distinctive feature relative to peer juniors at this stage. The Perpetua Resources adjacency provides geological credibility, with the explicit caveat that analogues do not guarantee equivalent deposit scale. FAST-41 designation gives Horse Heaven a structural permitting advantage if the resource case strengthens.

The conditions under which this thesis becomes more compelling are specific: a compliant tungsten or antimony resource, a Johnson Creek processing permit, or a definitive offtake agreement that validates the end-to-end domestic supply chain model. The conditions under which it becomes less compelling are equally specific: drilling results that fail to demonstrate continuous mineralisation at depth, capital constraints that force programme deferrals, or a policy shift that reduces the commercial urgency for domestic critical minerals. An investor who tracks those specific events rather than reacting to thematic sentiment will be better positioned to read each milestone as it arrives.

This article is for informational purposes only and should not be considered financial advice. Investors should conduct their own research and consult with financial professionals before making investment decisions. Forward-looking statements regarding resource definition, processing timelines, and policy conditions are speculative and subject to change based on market developments and company performance.