Melonite, merenskyite, and moncheite occur as minute grains (40 to less than 5 mu m) dispersed within the main sulfides (pyrrhotite, pentlandite, and chalcopyrite) in sulfide concentrations of the Ivrea-Verbano layered basic complex. Electron microprobe analyses indicate that melonite and merenskyite cover the whole range of Ni-Pd substitution, confirming the sofar inferred existence of a complete solid solution between these phases. Moncheite is much less abundant and always contains significant amounts of Pd and Ni. Substitution of Bi for Te is only occasional. Melonite is frequently found in paragenetic association with hessite, altaite, Bi tellurides, Ni-Co sulfarsenides, Au-Ag alloys (electrum), and irarsite.