R. G. Arnold and O. P. Malik
The NiS-S system above 980 degrees C; a revision (in An issue devoted to Canadian mineral deposits)
Economic Geology and the Bulletin of the Society of Economic Geologists (February 1975), 70(1):176-182

Abstract:
The NiS-S system above 980 degrees has been reinvestigated. The phase relations in the NiS-NiS ₂ portion of the system as indicated by Kullerud and Yund (1962) are confirmed, but the compositions of phases and reaction temperatures are refined.Phase relations in the NiS ₂ -S portion of the system are revised. Vaesite (NiS ₂ ) melts synthetically at 1,022 + or - 3 degrees C to two immiscible liquids, a nickel-rich liquid (L ₁ -- 52.0 + or - 1.8 wt % Ni) and a sulfur-rich liquid (L ₂ -- 0.5 + or - wt % Ni) as expressed by the reaction:heatingVaesite (NiS ₂ ) <--> L ₁ + L ₂ (vapor present P (sub S ₂ ) [asymp] 100 atm)1,022 + or - 3 degrees CThis is apparently the first syntectic reaction to be reported for sulfide systems.