Rare Earth Directory

Mine profile

Halleck Creek: location, owner, status and timeline (2026)

Development Wyoming

Halleck Creek, in northeastern Albany County, Wyoming, is the largest known US rare earth deposit by contained oxide, at about 8.7 Mt TREO (OSTI review, 2026). American Rare Earths (ASX: ARR) owns it and plans to start with the Cowboy State Mine on state land, with a pre-feasibility study scheduled for Q3 2026.

Verified through Oct 1, 2026

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Where is Halleck Creek?

Halleck Creek is in the central Laramie Mountains of northeastern Albany County, southeastern Wyoming. The project has two parts: the Cowboy State Mine area in the south on state land, and the Overton Mountain area in the north.

The Cowboy State Mine sits on 100% State of Wyoming surface and mineral rights, which the company says offers a streamlined permitting process. The broader Halleck Creek development, covering Overton Mountain, Red Mountain and Bluegrass, lies on federal land and minerals.

Wyoming has two other rare earth projects in this directory: Brook Mine in the north and Bear Lodge in the northeast.

Who owns Halleck Creek?

American Rare Earths Ltd (ASX: ARR) owns Halleck Creek through its US subsidiary Wyoming Rare (USA) Inc. The company is listed in Australia, has its US office in Lakewood, Colorado, and has been led by chief executive Mark Wall since Jan 5, 2026.

American Rare Earths also trades as American depositary receipts on the OTCQX (AMRRY) and as ordinary shares on the OTCQB (ARRNF). It describes its aim as moving from explorer to producer of rare earths in the US. Its other US project is La Paz in Arizona.

See American Rare Earths: what it does, projects, funding and status for the company profile.

What is the status and timeline of Halleck Creek?

Halleck Creek is in "Development": it has a JORC resource and a 2025 scoping study, and a pre-feasibility study is scheduled for Q3 2026. The company plans to file the Wyoming permit to mine in late 2026 and has talked of production around 2029.

  1. 2025

    An updated scoping study shows a JORC resource of 2.63 billion tonnes at 3,292 ppm TREO and a phase 1 NPV of $558M.

  2. May 2025

    12 months of groundwater baseline data collection begins at the Cowboy State Mine.

  3. Nov 13, 2025

    The chairman's AGM address sets a pre-feasibility study, state permitting and processing scale-up as 2026 goals.

  4. Jan 5, 2026

    Mark Wall becomes chief executive.

  5. Apr 2026

    The company awards a whole-of-property development assessment to an engineering firm.

  6. Q2 2026

    A 3,050 m core drilling campaign begins at the Cowboy State Mine.

Next milestones

  1. Q3 2026

    The pre-feasibility study is scheduled for delivery; check the company's ASX announcements for its release.

  2. Late 2026

    The Wyoming permit-to-mine application is planned to be filed.

  3. About 2029

    The company has talked of starting production (company target).

How big is Halleck Creek and what would it produce?

Halleck Creek has a JORC resource of 2.63 billion tonnes at 3,292 ppm TREO, about 8.7 Mt of contained oxide, the largest known in the US. The first phase, the Cowboy State Mine, would process 3 Mt a year over a 20-year life.

The grade is low, about 0.33% TREO, so Halleck Creek is large but lean. The main rare earth mineral is allanite in an A-type granite. The resource covers only part of the project area, and the 2026 core drilling program of 3,050 m at the Cowboy State Mine supports a later definitive feasibility study.

Halleck Creek resource and phase 1 scoping study
ItemFigureSource
JORC resource2.63 billion tonnes at 3,292 ppm TREOAmerican Rare Earths (2025 scoping study)
Contained TREOAbout 8.7 MtOSTI review (2026)
Phase 1 (Cowboy State Mine)3 Mt/yr base case; 20-year lifeAmerican Rare Earths
Phase 1 economicsAfter-tax NPV $558M at 10%; IRR about 24%American Rare Earths (scoping study)
Phase 2 (federal land)Mine life of more than 80 yearsAmerican Rare Earths

A scoping study is an early-stage estimate. OSTI notes that the scoping flowsheet would not be viable if the mine sold only a rare earth oxide concentrate, so the economics depend on further processing.

How would Halleck Creek be processed and who would buy the output?

American Rare Earths has released a preliminary processing flowsheet and will refine it in the Q3 2026 pre-feasibility study. No offtake agreement or processing site has been announced in the sources checked, and no government funding has been recorded.

In Apr 2026 the company awarded a whole-of-property development assessment to an engineering firm. It covers the Cowboy State Mine and later phases at Red Mountain, Overton Mountain and Bluegrass, and it is meant to set the roadmap for expansion.

The company has said it is considering a US stock market listing and that it aims to scale processing to meaningful product volumes. Its stated production ambition is around 2029, which is a company target and not a commitment.

What permits and community issues affect Halleck Creek?

The Cowboy State Mine needs a permit to mine from the Wyoming Department of Environmental Quality, which American Rare Earths plans to file in late 2026. Baseline work is advanced, with groundwater monitoring wells installed and 12 months of data collected from May 2025.

Because the first phase is on state land, the company expects a permitting path of about two years, shorter than for a federal project. Phase 2 on federal land would need a separate federal review.

No organized opposition, lawsuit or permit appeal was found in the sources checked. Local coverage in the Laramie Boomerang has focused on resource and technical progress. Water use and processing waste are the questions a permit application would have to address.

What government support has Halleck Creek received?

No federal or state funding is recorded for Halleck Creek in the sources checked. The project benefits indirectly from the state-land permitting route, and the US government has backed other rare earth projects with loans, grants and equity.

No federal support is recorded for Halleck Creek in the sources checked.

See the government support tracker for the companies that have received funding.

Questions about Halleck Creek

Is Halleck Creek the largest rare earth deposit in the US?

Halleck Creek is the largest known US rare earth deposit by contained oxide, about 8.7 Mt TREO according to OSTI. It is large but low grade, at about 0.33% TREO, and Mountain Pass has a much higher grade at 5.98%.

Where is Halleck Creek?

Halleck Creek is in the central Laramie Mountains of northeastern Albany County, southeastern Wyoming. The Cowboy State Mine is in the south of the project and the Overton Mountain area is in the north.

Who owns Halleck Creek?

American Rare Earths Ltd (ASX: ARR) owns Halleck Creek through Wyoming Rare (USA) Inc. The company's US office is in Lakewood, Colorado, and Mark Wall has been its chief executive since Jan 5, 2026.

Is Halleck Creek on federal land?

Phase 1, the Cowboy State Mine, is on 100% State of Wyoming land. The wider Halleck Creek development, including Overton Mountain, is on federal land and minerals and would need a federal review.

When will Halleck Creek start producing?

American Rare Earths has talked of production around 2029. It plans a pre-feasibility study in Q3 2026 and a permit-to-mine filing in late 2026, and has no finalized financing or offtake yet.

Sources and verification

Each profile lists its sources, a confidence grade and a verification date. Order of authority: official records (SEC filings, agency documents), company documents and technical reports, research papers, then independent press. Syndicated copies and reference works are labeled and are never the only source for a number. Company-reported figures are labeled as such, and non-binding deals are labeled "letter of intent" or "conditional".

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