American Uranium (ASX:AMU) will start hydrogeologic testing and resource development drilling at its Lo Herma in-situ recovery uranium project in Wyoming in the fourth quarter of the year, according to a Thursday filing with the Australian bourse.

The programs are designed to boost resource base growth and confidence in existing mineral resources, as well as validate the project's hydrogeology, the filing said.

The programs are expected to be incorporated into an updated mineral resource estimate and scoping study in 2026, according to the filing.

Shares fell 10% in midday trade Thursday.