American Rare Earths Ltd (ASX:ARR, OTCQX:ARRNF) has outlined a larger development case for its Cowboy State Mine in Wyoming, with an updated Scoping Study estimating an after-tax net present value (NPV) of about US$1.07 billion and a 26-year operating life.
The study assesses a 4.5 million tonne per annum operation, up 50% from the previous 3 million tonnes per annum case, with initial capital estimated at about US$900 million including contingency.
Average annual production of neodymium-praseodymium (NdPr) oxide is forecast at about 2,500 tonnes, a 36% increase from the 2025 base case, while the mine life has been extended from 20 to 26 years.
The case comes ater the company's first certified assay results from the initial six HQ core holes completed as part of its 2026 Feasibility Study drilling program at Cowboy State.
Larger first phase at Halleck Creek
Cowboy State Mine represents the first development phase of American Rare Earths' broader Halleck Creek Rare Earths Project , which hosts a JORC mineral resource of about 2.63 billion tonnes grading 3,292 parts per million total rare earth oxides.
The new mine plan envisages processing 4.5 million tonnes annually and producing about 2,500 tonnes of NdPr oxide each year, compared with about 1,833 tonnes in the previous study.
The updated case generates an after-tax internal rate of return of about 21% and an estimated payback period of 6.9 years, based on an assumed NdPr oxide price of US$151 per kilogram.
Development is planned around mining and mineral concentration at Cowboy State Mine, followed by hydrometallurgical refining at a separate facility in Wyoming.
Chief executive officer Mark Wall said the study provided a clearer picture of the project's first development phase while work continued to improve recoveries, infrastructure and processing configuration.
Building a US rare earth supply chain
American Rare Earths is also progressing work aimed at connecting Halleck Creek's resource with the downstream US permanent magnet supply chain.
A 50-kilogram concentrate sample is being tested by Novex in the US as part of work assessing oxide recovery and a potential pathway to NdPr metal production.
The company is targeting separated rare earth oxide from its pilot and demonstration program by late in the second quarter of 2027, while additional recovery optimisation work is being undertaken with Nagrom in Perth and Saskatchewan Research Council in Canada.
A prefeasibility study remains underway alongside permitting, infrastructure studies and further technical work, with American Rare Earths also advancing preparations supporting a potential Nasdaq listing.
The Scoping Study remains preliminary and does not establish Ore Reserves, with the production target based entirely on Indicated Mineral Resources.
