Archimedes’ truncated icosahedron
The hidden structure of geodes.
This is not a balloon… indeed it looks like one because the latter is a basic sphere. After Plato created his five solids, about two centuries later, Archimedes modified the structure of the icosahedron by truncating the twelve vertices. This geometric shape is the primary shape that structures a geode. We can distinguish between pentagons and hexagons.