Figure 1. Phase relations.

Phase diagram of the platinum–arsenic-bearing Fe-(Cu)-S systems determined at an S₂ partial pressure corresponding to the Fe_1−xS–S₂ liquid–vapour equilibrium20. Blue symbols—compositions of sperrylite-saturated Fe-(Cu)-S melts (~5,000–6,000 p.p.m. Pt). Red symbols—sperrylite compositions. Small black symbols—sperrylite-undersaturated melts analysed for Pt–As distribution and/or FIB sectioned in search of Pt–As nanophases and nanoparticles. The insets illustrate the compositional regions where macroscopic sperrylite (euhedral, bright) is stable and where (Pt–As)_n nanophases are found. Error bars are 2 sigma of the mean.