# Excavated dodecahedron

Excavated dodecahedron
Type Stellation
Index W28, 26/59
Elements
(As a star polyhedron)
F = 20, E = 60
V = 20 (χ = −20)
Faces
Star hexagon
Vertex figure
Concave hexagon
Symmetry group icosahedral (Ih)
Dual polyhedron self
Properties noble polyhedron, vertex transitive, self-dual polyhedron
Animation of an excavated dodecahedron (click to view)

In geometry, the excavated dodecahedron is a star polyhedron having 60 equilateral triangular faces. Its exterior surface represents the Ef1g1 stellation of the icosahedron. It appears in Magnus Wenninger's book Polyhedron Models as model 28, the third stellation of icosahedron.

## As a stellation

Stellation diagram Stellation Core Convex hull

Icosahedron

Dodecahedron

## Analogous faceting

It has the same external form as a certain facetting of the dodecahedron having 20 self-intersecting hexagons as faces. The non-convex hexagon face can be broken up into four equilateral triangles, three of which are the same size. A true excavated dodecahedron has the three congruent equilateral triangles as true faces of the polyhedron, while the interior equilateral triangle is not present.

The 20 vertices of the convex hull match the vertex arrangement of the dodecahedron.

The faceting is a noble polyhedron. With six six-sided faces around each vertex, it is topologically equivalent to a quotient space of the hyperbolic order-6 hexagonal tiling, {6,6} and is an abstract type {6,6}6. It is one of 10 abstract regular polyhedron of index two with vertices on one orbit.[1][2]

## References

1. ^ Regular Polyhedra of Index Two, I Anthony M. Cutler, Egon Schulte, 2010
2. ^ Regular Polyhedra of Index Two, II  Beitrage zur Algebra und Geometrie 52(2):357-387 · November 2010, Table 3, p.27
(Convex) icosahedron Small triambic icosahedron Medial triambic icosahedron Great triambic icosahedron Compound of five octahedra Notable stellations of the icosahedron Regular Uniform duals Regular compounds Regular star Others The stellation process on the icosahedron creates a number of related polyhedra and compounds with icosahedral symmetry.