Deriving a Bilunabirotunda from Rhombic Solids
This Demonstration shows a derivation of a bilunabirotunda (Johnson solid J91) from golden rhombic solids.
A triacontahedron is prolonged in two directions; then some oblate rhombohedra are removed. In the next step, two halves of a rhombic dodecahedron of the second kind are removed. The obtained "rhombic" solid is a rhombic "approximate" of a bilunabirotunda. The bilunabirotunda inscribed in the "rhombic" solid has a deficit of 4 pentagonal cups, while triangular pyramids annihilate one another.