I hand-build clay models to create the plaster molds that hold these Pâte de Verre geodes. The glass used is 100% salvaged shelf glass that I hand crushed and sifted.
Sizes are roughly
Small - 2.5" Medium - 3" Both have larger crystals in the center, about the size of rock salt
Large - 3.5" and has small crystals in the center (more like sugar)