The relevance of anisotropic interactions in colloidal systems has recently
emerged in the context of rational design of novel soft materials. Theoretical
studies have predicted the possibility of a gas-liquid phase separation
confined at low densities and the formation of empty liquids and equilibrium
gels in low-valence systems. Here we provide experimental evidence of this
scenario in Laponite, a complex colloidal clay with discotic shape and
anisotropic interactions. We also report simulations of a patchy model for
Laponite platelets, able to reproduce the observed experimental phase diagram
and structural properties, confirming the crucial role of the reduced valence