English: A collection of lithophysae "thundereggs" from many locations showing the outside "sutures and plates" where fractures reached the surface. On cooling the cristobalite needle structure was no longer viable so the SiO2 reverted to other forms. some have smaller "eggs" attached. Many "eggs" have ridges where the steam pressed the rhyolite away. Others cooled and allowed the matrix ro press them flat or even indent them.