Fine grinding of silica was carried out in a jet mill, varying operational parameters such as feed rate, classifier rotational speed and grinding pressure. The size reduction of silica was intensive as the jet mill is energy intensive. Abrasive and destructive breakage mechanisms took place varying according to the operating conditions of the jet mill. The minimum particle size obtained was 3.15 mu m with a span value of 1.30. The circularity value of the ground silica ranged from 1.29 to 2.02. Particles ground at lower grinding pressure exhibited more or less spherical shapes whilst at higher grinding pressure, elongated particles with sharp edges were produced. (C) 2007 Elsevier Ltd. All rights reserved.