American Rare Earths boosts Mineral 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 Rare Earths project in Wyoming.  

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

The updated mineral resource estimate (MRE) for the Cowboy State mine area is approximately 547.5 million tonnes using a TREO cut-off grade of 1,000ppm, the company said.  

The MRE update incorporates the 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 Mineral Resource Estimate presented in the February 2025 updated CSM Scoping Study. 

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

In October 2025, ARR received two drilling permits from the Wyoming Department of Environmental Quality. 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, the company noted.

Last year, Cowboy State mine was approved for up to $7.1 million in state-backed non-dilutive funding through a 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. 

Australian-headquartered ARR shares closed the day up 6%. The company has a A$249.3 million ($161m) market capitalization.