A process for preparing high purity superfine powders of less than 0.5µ diameter of Mo, W, Nb, Zr, Cu, Zn, Co, Ni and In by first producing their fluoride or a double fluoride with ammonium and then decomposing them under heat in a hydrogen-containing stream. Features of the present process are that the double fluoride of the metals with ammonium is faster in crystal growth than the fluoride, recrystallization of these salts can be repeated as desired when a high purity of the metals is required, and particles of a uniform size can be obtained easier.