Synthetic "Cooperite", "Braggite", and "Vysotskite" in the system PtS-PdS-NiS at 1100°C, 1000°C, and 900°C

¶Results of experimental investigations in the dry system PtS-PdS-NiS at 1100°C, 1000°C, and 900°C are presented. The phases observed at 1100°C are "cooperite" and a melt, at 1000°C "cooperite", "braggite", and a melt and at 900°C "cooperite", "braggite", "vysotskite", Ni_1‑xS, and a melt. At 1100°C the maximum solubility of Ni in ideal, Pd-free "cooperite" is 2.7 atomic per cent and the Pd-content limit in Ni-free "cooperite" is 12.8 atomic per cent. At 1000°C the maximum solubility of Ni in ideal, Pd-free "cooperite" is 3.3 atomic per cent and the Pd-content in Ni-free "cooperite" is 13.7 atomic per cent. The "braggite" composition ranges from Pt_0.56Pd_0.38Ni_0.06S and Pt_0.59Pd_0.41S in a Ni-saturated and Ni-free environment respectively to Pt_0.18Pd_0.80Ni_0.02S and Pt_0.14Pd_0.86S respectively. At 900°C the maximum Ni-content in ideal Pd-free "cooperite" is 3.1 atomic per cent and the Pd-limit in Ni-free "cooperite" is 12.5 atomic per cent. The "braggite" composition ranges from Pt_0.59Pd_0.29Ni_0.12S and Pt_0.60Pd_0.40S for a Ni-saturated and Ni-free environment respectively, to Pd_0.91Ni_0.09S and PdS respectively. The Ni-content in "braggite" and "vysotskite" increases slightly with increasing Pt/Pd ratios and is higher at 900°C than at 1000°C. Comparison of experimental trends with cooperite, braggite, and vysotskite analyses from the literature implies high temperatures of formation for Pt-Pd-Ni sulphides in placers if Ni-saturation is assumed.