The flotation separation of pyrite from pyrophyllite using oxidized guar gum (OGM) as depressant has been studied through flotation tests, adsorption and FTIR spectra measurements. Flotation tests on a single mineral and mixed binary minerals show that the reagent schedule of depressant OGM 50 mg/L, collector SIBX (sodium isobutyl xanthate) 0.2 mmol/L and frother DIDE (diethyleneglycol dimethyl ether) 7 mg/L at pH 6 could achieve selective flotation separation of pyrite from pyrophyllite (a concentrate with S grade of 48.0% and recovery of 86.9% was achieved by the mixed binary minerals flotation), which indicate that OGM has selective depression effect on pyrophyllite Minerals while has little depression effect on pyrite. Adsorption and FTIR spectra measurements illustrate that OGM could absorb more strongly on pyrophyllite surface than on pyrite surface, and the interaction of OGM with the pyrophyllite surface consists of a dominant chemisorptions while the OGM cannot interfere with the FTIR spectrum of pyrite. This is the reason why OGM has excellent depression selectivity for pyrophyllite and negligible effect on pyrite flotation. (C) 2017 Elsevier B.V. All rights reserved.