Single crystalline samples of bismuth tellurite were implanted with 800 keV Au + and 450 keV Ag + ions to fluences between 5x10 1 5 and 2.5x10 1 6 cm - 2 at room temperature. The samples were annealed at temperatures of 600 o C for Au, 450 o C for Ag and 500 o C for Au/Ag implanted crystals. Strong optical absorption maxima at about 630 nm yielding Au-implanted samples and at about 570 nm for Ag-implanted samples indicate the formation of noble metal clusters. For Au and Ag co-implanted samples the optical absorption spectrum shows a complex structure with a main maximum around 600 nm which is tentatively associated with mixed Au/Ag clusters. The average cluster radii were calculated to be in the range of 2-10 nm depending on the implanted ion species.