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Bilunabirotunda

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Bilunabirotunda
Bilunabirotunda 7847
Johnson solid J91
TypeJohnson Solid
Panels 8 × Geomag triangle panel icon
2 × Geomag square panel icon
4 × Geomag pentagon panel icon
Rods 26 × Geomag rod icon
Spheres 14 × Geomag ball icon
Author PolyClare 17:47, 9 January 2008 (UTC)


This polyhedron was the 91st detailed in Johnson's seminal paper, consequently it's often notated J91, the 91st Johnson Solid. It is an elementary polyhedron that may not be formed from other basic Platonic, Archimedean, and Johnson solids.

Johnson termed the complex of two equilateral triangles adjacent to opposite sides of a square a "lune": Lune. And recalled that the sequence of 5,3,5,3 is known for appearing on a Pentagonal Rotunda (a.k.a. J6), which is more elementary than the Icosidodecahedron. Therefore the two "lunes" and the two "rotunda" vertices justify Johnson's termonology bi-luna-bi-rotunda for this solid.

Six bilunabirotundas may be used to form the lovely Stewart's 6J91(P4), which may be utilized further to form the central 6-way hole for the fabulous Lunar-holed Rhombicosidodecahedron, Stewart's E5/6J91(P4).

These models were built using Geomag Pastelles.


Other views Edit

Related links & references Edit

  • Norman W. Johnson, "Convex Solids with Regular Faces", Canadian Journal of Mathematics, 18, 1966, pages 169–200.

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