The depression mechanism of a combination of ZnSO₄ and Na₂CO₃ on talc during chalcopyrite and molybdenite flotation was investigated in-depth using flotation tests, solution speciation calculations, and various characterization techniques. Flotation tests indicate that the effective depression of talc flotation occurred in the pH range of 7-9. In this pH range, speciation calculations for the mixed solution of ZnSO₄ and Na₂CO₃ showed that the Zn₅(OH)₆(CO₃)₂ precipitate was the predominant zinc-bearing species, which was further proven by X-ray diffraction and infrared spectroscopy measurements. Zeta potential measurement highlighted that the Zn₅(OH)₆(CO₃)₂ precipitate was positively charged while the talc surface was negatively charged in the pH range where talc depression occurred. X-ray photoelectron spectroscopy and field emission scanning electron microscopy confirmed the presence of the zinc-bearing precipitate on the surface of the talc particles treated by the combination of ZnSO₄ and Na₂CO₃. These findings suggested that heterocoagulation between the formed Zn₅(OH)₆(CO₃)₂ and talc occurred mainly due to the electrostatic attraction, thereby leading to the depression of talc flotation.