In a process for metakaolin production from kaolinitic clay by crushing, drying and calcining, calcination is carried out at 700-1086 deg C in a fraction of a second in a pulsed reactor and the resulting metakaolin is cooled to below 600 deg C at the reactor outlet. Preferably, the pretreated clay has a particle size of <= 1.5 (especially <= 0.9) mm. and may be fed together with combustion air and optionally an auxiliary fuel to the combustion chamber of the pulsed reactor or may be fed directly to the resonance tube of the reactor.
