Buckminsterfullerene (C60) is the smallest fullerene in which no two pentagons share an edge (which can be destabilizing). It is also the most common in terms of natural occurrence, as it can often be found in soot. The structure of C60 resembles a round soccer ball of the type made of hexagons and pentagons, with a carbon atom at the corners of each hexagon and a bond along each edge. The C60 molecule has two bond lengths. The 6:6 ring bonds (between two hexagons) can be considered "double bonds" and are shorter than the 6:5 bonds (between a hexagon and a pentagon).