Triuridium was a substance which was mined on Farius Prime in the early 24th century. By 2336, almost all of Farius Prime's triuridium had been mined and exported. This information allowed Doctor Jo Stern, when she found triuridium dust on Commander Samir al-Halak, to deduce that he had to have picked it up in or near one of those old mines. (TLE novel: Well of Souls)