Pentlandite phase relations in the Fe–Ni–S system and notes on the monosulfide solid solution

A curve relating composition of synthetic pentlandite with interplanar spacing was determined experimentally as follows: d 115 = 1.9407 – 0.0023x + 0.0077x 2 , where x represents the iron to nickel weight ratio with d 115 measured in Å and the sulfur content is fixed at 33.0 5 wt %. The following iron, nickel, and sulfur solid solubility limits of pentlandite were determined:[Formula: see text]X-ray powder patterns of monosulfide solid solution heated at 500 and 400 °C with a composition (wt %) of 18.8 Fe, 43.8 Ni and 37.4 S showed a modulated structure. A solvus interrupts the monosulfide solid solution at 275 ± 10 °C and the approximate composition in wt %: Fe = 22. 5 , Ni = 40, and S = 37. 5 .The relatively common occurrence of the pyrite–pentlandite assemblage in nickel ores shows that the solid state reactions attendant upon cooling of these ores, proceed to temperatures at least below 200 °C.