The stability fields of michenerite and merenskyite have been defined above about 450 degrees C. Michenerite forms an extensive but narrow solid-solution field by substitution between Bi and Te from Pd (sub 0.99) Bi (sub 0.79) Te (sub 1.22) to Pd (sub 0.95) Bi (sub 1.11) Te (sub 0.94) ; Pd ranges from 31.5 to 33.2 atomic percent. The Bi-rich end of michenerite melts incongruently at 489 degrees + or - 3 degrees C, and the Te-rich end melts at 501 degrees + or - 3 degrees C to Bi-rich kotulskite and liquid.Merenskyite forms a more extensive solid-solution field than michenerite and varies from PdTe 2 to Pd (sub 1.05) Te (sub 1.34) Bi (sub 0.61) . Substitution is mainly of Bi for Te and subordinately of Bi and Te for Pd. Merenskyite has the stoichiometric formula of Pd(Te,Bi) 2 when associated with Te and tellurobismuthite but becomes Pd-rich when associated with wehrlite and michenerite. A complete solid solution exists between merenskyite and kotulskite from 575 degrees + or - 10 degrees to 710 degrees + or - 10 degrees C. With rising temperature merenskyite retreats toward PdTe 2 , which melts at 740 degrees + or - 3 degrees C.