Solutions of the synthetic clay Laponite are strongly viscoelastic, even at
very low particle concentrations. The formation of a gel, evidenced by the
existence of a fractal network, has been invoked in explaining the viscoel
asticity. We study the structure and viscosity of Laponite using static lig
ht scattering and rheometry. Contrary to previous observations, we find no
evidence of a fractal-like organization of the colloidal particles, provide
d the dispersion is prepared carefully. The results show that there is no r
elation between the apparent fractal dimension and the viscoelasticity, A p
ossible interpretation of our results is that Laponite solutions form collo
idal glasses, rather than gels.