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This last example gives a hint at the diversity of polyhedra that can occur in solid state compounds, as well as how they can be interpreted in terms of simpler ones. This is the Friauf polyhedra, which serves as a key building block in a variety of intermetallc phases. As is highlighted here, this 16-vertex unit can be broken down into two parts. First is a 12-vertex cage built from four hexagons and four triangles (filled with blue). It is called a truncated tetrahedron as it can be created from a tetrahedron by cutting off each of the corners to leave new triangular faces. The second part is a tetrahedron whose vertices each lie over the hexagonal face of the truncated tetrahedron (the tetrahedron’s corners are drawn here as connected to the central point of the polyhedron, with the actual edges of the tetrahedron not being shown for clarity).