
The above encasement of an IVM sphere (that the sphere appears to really be made of tiny dots is not unfortunate in this context), outlined in black, is the rhombic dodecahedron.
The long diagonals of each diamond facet (one is shown in red) form an octahedron, while the greens (short diagonals) form a cube. The relative volume ratios are 6:4:3.

Below is the shape most people think about when they hear the word "dodecahedron," if they think of a shape at all. Centuries of Platonic bias stacked the deck such that "dodecahedron" means the Platonic one, kind of like when some USAers say "Americans" and just mean themselves.
