In September 2018, the Idrija mine was chosen as the second field trial for UNEXMIN, following the Kaatiala trials. The UX-1 robot, which had been upgraded since the previous trials, once again demonstrated its proficiency in navigating through shafts and underwater tunnels while executing tasks such as control and 3D mapping. Since the Idrija mine is a UNESCO Heritage site, it was crucial that the UNEXMIN technology functioned in a non-damaging and non-contact manner as any damage to the mine could not be tolerated.

The Idrija mine has been explored for mercury since 1490 until its closure in 1995. This mine contains significant hydrothermal ore deposits of cinnabar and native mercury, both of which are present in sedimentary rocks. The mine spans a vast network of tunnels totalling about 700km, and its global importance is undeniable.

See the following YouTube video about the mission: