A silica fume that is condensed to become a colloidal powder. About 1% in water produces an effect called non-Newtonian viscosity. The viscosity builds up at low shear rates yet it gels. Such a material will help suspend and gel a glaze to make it easier to apply thick layers on very thin ware.
Silica/Quartz Quartz is very abundant and there are many grades and name brands.