Silica was ground in an oscillating mill at various grinding period to study the mechanochemical effect in fine grinding process. The ground particles exhibited massive size reduction where the volume moment diameter of 5.56 mu m was reached within 600 s. Aggregation of fine particles was very pronounced when it was ground for 600 s due to high surface energy. Aggregation of fine particles caused the ground particles to exhibit poly-modal particle size distribution. Line broadening and reduction of diffractogram peak intensity were observed. Amorphization rate up to 16.9% was exhibited by the particle ground for 600 s. Preferential breakage of plane was observed where (101) and (111) was easily distorted compared to (110) and (200). Rapid reduction of crystallite size was observed at early stage of grinding until it reached a plateau at 5 nm at 600 s whilst the change in lattice strain was 0.5%. (C) 2006 Elsevier B.V. All rights reserved.