American Rare Earths (ASX:ARR) completed the production of a mixed rare earths oxide from Halleck Creek in Wyoming using the updated preliminary pre-feasibility study mineral processing flowsheet, according to a Tuesday filing with the Australian bourse.

The process involved using the material from the impurity removal testing campaign, precipitating a mixed rare earth oxalate, and then creating mixed rare earth oxide powder, the filing said.

Solvent extraction computer simulation is ongoing, per the filing.

Shares fell 3% in morning trade on Tuesday.