• Synchrotron X-ray powder diffraction with Rietveld refinement successfully quantified pyrrhotite superstructures (4C, 5C, 6C) in a copper–gold ore, revealing flotation recovery order 4C<6C<5C.
• DFT calculations showed that the 4C superstructure has the closest Fe 3d and S 3p band centers to the Fermi level, indicating higher surface reactivity and hydrophilicity.
• The 4C pyrrhotite promotes formation of hydrophilic Fe-OH/Fe-OOH species, while 5C and 6C favor dixanthogen formation, increasing hydrophobicity and floatability.
• The study provides a direct correlation between electronic structure and flotation behavior, offering a basis for optimizing pyrrhotite depression in industrial flotation.