Heterocoagulation between mineral particles, which is also called slime coating, is an intractable problem that deteriorates the separation efficiency in mineral flotation. To date, although diverse methods of characterizing mineral heterocoagulation are available, there is short of quantitative characterization. In the present work, a novel method named Mineral Heterocoagulation Quantifying System was developed to quantitatively characterize heterocoagulation. The heterocoagulation between coal and quartz particles was measured at different pH values and sodium hexametaphosphate (SHMP) concentrations. With the heterocoagulation degree given by the Mineral Heterocoagulation Quantifying System at different time, the heterocoagulation kinetics was analyzed for the first time. It was found that the heterocoagulation rate in the present work can be fitted to a classical first-order model. The zeta potential distribution measurements were also conducted to characterize heterocoagulation and the results were consistent with that given by the Mineral Heterocoagulation Quantifying System. The inter-particle force calculation based on the Deyaguin-Landau-Verwey-Overbeek (DLVO) theory was conducted to validate the heterocoagulation results.