The influence of attrition milling on the thermal decomposition of kyanite ((Al2O3SiO2)-Si-.) to mullite (3Al(2)O(3)(.)2SiO(2)) and SiO2, and its subsequent sintering, was studied. A commercial kyanite was attrition-milled for times up to 12 h. Dilatometry confirmed that as-received unmilled kyanite decomposes between 1300degrees and 1435degreesC. The decomposition reaction is slow initially and accelerates during the later stages until about one-half of the decomposition occurs in the last 35degreesC. For the attrition-milled kyanite, the onset decomposition temperature decreases, the transformation temperature interval is reduced, and both the decomposition reaction and subsequent sintering are accelerated. A dense microstructure of fine equiaxed mullite grains in the 1 mum size range, evenly dispersed in a glassy matrix, is obtained by sintering the attrition-milled kyanites. These results are explained in terms of the energy accumulated during attrition milling, a reduction of the milled kyanite particle size, and the presence of a liquid phase during sintering.