To develop a binary colloidal system with a slight index of refraction mismatch suitable for light scattering studies, pure silica particles synthesized by the method of Stober were mixed with aluminosilicate colloids synthesized using a novel approach. With this, index-matching for one component allowed extraction of the spatial distribution of the other. In addition, it was observed that by varying the solvent, interactions between colloids could be tuned from purely repulsive to weakly attractive. (C) 2003 Elsevier Inc. All rights reserved.