Polysaccharide reagents are frequently used in the mineral processing industry to improve the grade of the concentrate by depressing the naturally floatable gangue. A microflotation study showed that at an ionic strength of 10(-3) M KNO3, the dosage, molecular weight, and chemical composition of polysaccharide depressants affect their depressing action on talc. Viscosity readings for four carboxymethylcellulose (CMC) reagents and three modified guar gum reagents are reported, and estimates of the molecular weight of the CMCs are calculated. The natural floatability of talc was diminished when guar-based polymers were added to the system. Moreover, the depression of talc was increased as the guar molecular weight was increased. Strong depression of talc was achieved at a relatively low guar dosage; higher dosages did not further increase this depression. At 10(-3) M KNO3, the CMCs were ineffective depressants of talc. No systematic change in talc depression for differing molecular weight CMCs was observed. A small increase in depression was observed when the concentration of CMC was increased. A mechanism is proposed for the polymer-talc interactions based on these preliminary studies and information from similar studies in literature. (C) 2000