Bauxite, particularly high alumina bauxite, and brucite are used as flame-retardants in non-aqueous organic polymer formulations particularly for electric insulation or sheathing or encapsulation, and also in bitumen. The formulations are suitable for shaping e.g. by casting, moulding or curing at temperatures of 150° C. or 200° C. Water resistance and other properties including cost of bauxite and brucite compare favourably with the conventional flame-retardant aluminium trihydrate.