American Rare Earths (ASX:ARR) updated its mineral resource estimate for the Cowboy State Mine area within its Hallack Creek rare earths project in Wyoming, reclassifying indicated resources by 68.4 million tonnes, according to a Wednesday Australian bourse filing.

The updated mineral resource estimate for the area is around 547.5 million tonnes using a total rare earths oxide cut-off grade of 1,000 parts per million (ppm), the filing said. The indicated resource was 391.4 million tonnes, and the inferred resource was 156.1 million tonnes.

Additional mapping associated with the channel sampling expanded the resource area to increase the Cowboy State Mine mineral resource estimate by around 4.5 million tonnes, per the filing.

A standout sample from summer exploration and mapping in the area contained a record high assay grade for the entire project, with a total rare earth oxide grade of 13,816 ppm.

American Rare Earths' shares rose past 2% in recent trading on Wednesday.