The Fe-Ni-S system at 725 degrees C was studied by means of dry synthe
ses in evacuated silica glass tubes and microprobe/textural analyses.
Contrary to previous beliefs it is dominated by an extensive solid sol
ution field of (Ni,Fe)(3+/-x)S-2 (up to 33 at % Fe) which coexists wit
h sulphide melt; mss does not coexist with melt at this temperature.