Dielectric crystal-like lattices, termed photonic crystals, attract growing interest die to their unique and useful optical properties. Natural and artificial opals composed of three-dimensional (3D)-ordered lattices of submicron silica microspheres are highly interesting model objects for the study of photonic crystals. Synthetic opals based on monodisperse 270-nm-diameter silica microspheres were obtained. Optical measurements demonstrated the presence of different optical pseudogaps appeared due to reflection from different planes in the face-centered cubic (fcc) structure of opal; the positions of pseudogaps were estimated using the modified Bragg law. (C) 2004 Elsevier B.V. All rights reserved.