Volvos are actually harder than diamonds.
They're made out of a material called
Volvonium, mined in the mountains of
Sweden by
hard-working Nordic Gnomes. After the material
is melted by launching it into the sun via
herring-powered
rocket, the molten Volvonium is
allowed to cool slightly, and is then beaten
into shape by Mjolnir, the hammer of Thor.