Its dual polyhedron is the rhombic dodecahedron. In geometry, the rhombic dodecahedron is a convex polyhedron with 12 congruent rhombic faces. The trapezo-rhombic dodecahedron is a convex polyhedron with 6 rhombic and 6 trapezoidal faces. The "rhombic dodecahedron" is a zonohedron with twelve rhombic faces and octahedral symmetry. This pattern also approaches the rhombic dodecahedral honeycomb or trapezo-rhombic dodecahedral honeycomb. The remaining 12 octahedral cells project onto the faces of the rhombic dodecahedron. Some minerals such as garnet form a rhombic dodecahedral crystal habit. The remaining 12 octahedral cells project onto the 12 rhombic faces of the rhombic dodecahedron. The elongated dodecahedron and trapezo-rhombic dodecahedron variations, along with the rhombic dodecahedra, are space-filling. The graph of the rhombic dodecahedron is nonhamiltonian. The set of vertices can be considered as the edges of a rhombic dodecahedron. This had a surface structure covered with small hexagonal and rhombic bumps. Stewart Coffin has been creating puzzles based upon the rhombic dodecahedron since the 1960s.