a method for dewatering mineral slurries employing a copolymer of diallyldimethlylammonium halide and a vinyl alkoxysilane , which is preferably a copolymer of diallyldimethylammonium chloride and vinyltrimethoxysilane as a coagulant is disclosed . the method for dewatering mineral slurries containing water comprising the steps of : feeding said mineral slurry into a thickener , treating said mineral slurry with an effective amount of a coagulant which comprises a copolymer of halide and a vinyl alkoxysilane ; allowing the water to separate from the mineral slurry , withdrawing the water from said thickener and discharging said mineral products from said thickener . mineral slurries which can be effectively treated are copper and taconite . the above - mentioned method may also include treatment with a flocculant in conjunction with the coagulant .