American Rare Earths boosts resource estimate for Cowboy State mine

American Rare Earths (ASX: ARR) announced Wednesday an updated mineral resource estimate for the Cowboy State mine (CSM) area within its flagship Halleck Creek project in Wyoming.

American Rare Earths’ subsidiary, Wyoming Rare, holds the Halleck Creek project, which was ranked in 2023 as one of the world’s top 10 rare earth projects measured in total rare earth oxides (TREOs).

The latest resource estimate for the Cowboy State mine area shows 547.5 million tonnes in TREOs using a cut-off grade of 1,000 parts per million (ppm). This incorporates results from 18 additional channel samples and coincides with the acquisition of two new exploration drilling permits.

The channel sample results enabled reclassification of approximately 63.9 million tonnes to the indicated category from the inferred category from the resource estimate presented in the February 2025 scoping study, ARR said.

Additional mapping associated with channel sampling expanded the resource area to increase the CSM mineral resource estimate by approximately 4.5 million tonnes, it added.

In October 2025, ARR received two drilling permits from the Wyoming Department of Environmental Quality. A total of 27 drill hole locations were permitted across the CSM area in preparation for in-fill drilling required for future technical studies beyond the forthcoming prefeasibility study.

Last year, Cowboy State mine was approved for up to $7.1 million in state-backed grant. The funding agreement was reached with support from the Wyoming Energy Authority and the University of Wyoming Energy Resources Council with the mission to support projects to advance the state’s energy economy.

The Australia-headquartered rare earth miner closed the day up 6%, with a A$249.3 million ($161 million) market capitalization.