The invention relates to a process for preparing a silicate of an element chosen from alkali metals, alkaline-earth metals or rare earths, comprising a reaction between silica and a sulfate of said element in a reactor equipped with at least one submerged burner within a molten mass, said submerged burner being fed with a gas containing oxygen, an excess of fuel/reducing agent being introduced into the reactor relative to the oxygen effectively consumed. The process allows the reaction to be carried out satisfactorily and at relatively low temperature.