This work reports on process-induced impurities in rare-earth ion: Dy3+-doped selenide chalcogenide glasses, which are significant materials for active photonic devices in the mid-infrared region. In particular, the effect of contamination from the silica glass ampoule containment used in chalcogenide glass synthesis is studied. Heat-treating Dy-foil-only, and DyCl3-only, separately, within evacuated silica glass ampoules gives direct evidence of silica ampoule corrosion by the rare-earth additives. The presence of [Ga2Se3] associated with [Dy] on the silica glass ampoule that has been contact with the chalcogenide glass during glass melting, is reported for the first time. Studies of 0-3000 ppmw Dy3+-doped Ge16.5As9Ga10Se64.5 glasses show that Dy-foil is better than DyCl3 as the Dy3+ additive in Ge-As-Ga-Se glass in aspects of avoiding bulk crystallization, improving glass surface quality and lowering optical loss. However, some limited Dy/Si/O related contamination is observed on the surfaces of Dy-foil-doped chalcogenide glasses, as found for DyCl3-doped chalcogenide glasses, reported in our previous work. The surface contamination indicates the production of Dy2O3 and/or [= Si-O-Dy=]-containing particles during chalcogenide glass melting, which are potential light-scattering centers in chalcogenide bulk glass and heterogeneous nucleation agents for alpha-Ga2Se3 crystals.