A mathematical model was developed for coal-coal pyrite separation by selective flocculation technology. The model predicted that selectivity is primarily governed by polymer adsorption, although improvements in selectivity may also be obtained by controlling the polymer dosage when the selectivity in polymer adsorption is not very high. Selectivity predicted for coal-coal pyrite-cationic polyacrylamide flocculant was in agreement with the experimental results. Poor selectivity achieved was attributed to hetroflocculation and kaolinite associated with coal and coal pyrite samples.