Abstract: A cordierite honeycomb structure having a coefficient of thermal conductivity of not less than 0.035 J/cm..degree.K.sec, a porosity of not more than 16%, and a coefficient of thermal expansion of not more than 1.0.times.10.sup.-6 /.degree.C. at 40 to 800.degree.0 C. is described. A process for producing a cordierite honeycomb structures, involves at least the steps of: mixing powders of kaolin, talc, and other starting materials for cordierite together so as to provide a chemical composition of cordierite; extruding the mixture; and firing the extrudate, wherein the kaolin has an average particle diameter of not more than 5 .mu.m and such a particle size distribution that the proportion of particles with diameters of less than 1 .mu.m is 10% by weight and the talc has an average particle diameter of not more than 10 .mu.m and such a particle size distribution that the proportion of particles with diameters of less than 1 .mu.m is not more than 5%.

Abstract: A cordierite honeycomb structure having a coefficient of thermal conductivity of not less than 0.035 J/cm.multidot..degree.K..multidot.sec, a porosity of not more than 16%, and a coefficient of thermal expansion of not more than 1.0.times.10.sup.-6 /.degree.C. at 40.degree. to 800.degree. C. A process for producing a cordierite honeycomb structures, involves at least the steps of: mixing powders of kaolin, talc, and other starting materials for cordierite together so as to provide a chemical composition of cordierite; and extruding the mixture; and firing the extrudate, wherein the kaolin has an average particle diameter of not more than 5 .mu.m and such a particle size distribution that the proportion of particles with diameters of less than 1 .mu.m is 10% by weight and the talc has an average particle diameter of not more than 10 .mu.m and such a particle size distribution that the proportion of particles with diameters of less than 1 .mu.m is not more than 5%.

Abstract: An unfired recycled material recovered in the course of the production of a cordierite ceramic body is comminuted to prepare a comminuted material. The comminuted material is then subjected to size separation to remove fine particles with diameters of less than 1 mm from the comminuted material while retaining coarse particles with diameters of not less than 1 mm. Water is added to the comminuted material with particle diameters of not less than 1 mm, and the mixture is kneaded to prepare a reprocessed clay. The reprocessed clay is formed into a shape which is then fired to prepare a cordierite ceramic body.