Treatment of mineral particles

The present invention relates to the treatment of mineral particles. In particular, it relates to the heat treatment by flash calcining of mineral particles suitable to be employed as coating, filler and extender materials in products such as papers, polymers, paints, cements, concretes and the like. Such minerals include, for example, clays especially kaolins processed or produced by various processes such as grinding or precipitation. A method of heat treating kaolin particles which includes the steps of establishing in a furnace a heating zone suitable to calcine the particles and passing the particles rapidly through the heating zone whereby the particles are flash calcined in the heating zone, wherein the furnace is of the kind in which a toroidal fluid flow heating zone is established and the particles are heated in the said heating zone to a temperature of at least 800° C. but not greater than 1100° C. by application to the particles of a temperature increase rate greater than 10Celsius degrees per second to give a rapid blistering of the particles caused by rapid dehydroxylation of the kaolin and wherein the particles have a residence time of less than 1 second in the said toroidal fluid flow heating zones.