41. Note the duality between the cube and the octahedron, and between the dodecahedron and the icosahedron . 42. The icosahedron is unique among the Platonic solids in possessing a dihedral angle not less than 120? 43. These all have icosahedral symmetry and may be obtained as stellations of the dodecahedron and the icosahedron . 44. The lattice has two basic structure units the B 12 icosahedron and the B 6 octahedron. 45. This polyhedron is the seventeenth stellation of the icosahedron , and given as Wenninger model index 42. 46. A truncation operation, repeatedly applied to the great icosahedron , produces a sequence of uniform polyhedra. 47. It has a related alternation honeycomb, represented by ?!, having icosahedron and tetrahedron cells. 48. The icosahedral shape is derived from the structure of an icosahedron which has 20 equilateral triangular faces. 49. The right one looks like it might be a subdivision surface generated by an actual truncated icosahedron . 50. A regular icosahedron is the optimum way of forming a closed shell from identical sub-units.
