A new form of cristobalite, collected in the form of spheroidal particles as the result of hot corrosion of clear fused silica ampoules, has been studied by X-ray diffraction, scanning and transmission electron microscopy. The transparent or translucent spherulites have a round but flattened shape, one vortex and a core made of nanosheets, perpendicular to the surface, organized in a nearly radial pattern. The electron diffraction study evidenced a single phase material with a pseudo-cubic supercell (a(sp) approximate to b(sp) approximate to c(sp) approximate to 14.1 angstrom and a F-type centred lattice) corresponding to an eight-fold multiplicity of the cristobalite cell. The TEM study evidenced twinning domains and intergrown polytypes, similar to those usually observed in the beta ->alpha cristobalite-type transition and cristobalite -> tridymite modifications. A formation mechanism of these cristobalite spherulites is proposed on the basis of a salt attack by a doping effect and the formation of droplets from a liquid state of silica. (C) 2011 Elsevier B.V. All rights reserved.