regular icosahedron

A hemi-icosahedron is an abstract regular polyhedron, containing half the faces of a regular icosahedron.

A regular icosahedron is the optimum way of forming a closed shell from identical sub-units.

This compound polyhedron is also a stellation of the regular icosahedron.

For example, HIV is enclosed in a regular icosahedron.

This die is in the form of a regular icosahedron.

Inside a Magic 8-Ball, various answers to yes-no questions are inscribed on a regular icosahedron.

However, neither the regular icosahedron nor the regular dodecahedron are amongst them.

Many viruses, such as the herpes virus, have the shape of a regular icosahedron.

The 6-orthoplex can be projected down to 3-dimensions into the vertices of a regular icosahedron, as seen in this 2D projection:

A regular icosahedron: a solid having 20 plane faces, all of them equilateral triangles.