Great inverted retrosnub icosidodecahedron

The great inverted retrosnub icosidodecahedron or girsid, also called the great retrosnub icosidodecahedron, is a uniform polyhedron. It consists of 60 snub triangles, 20 additional triangles, and 12 pentagrams. Four triangles and one pentagram meet at each vertex.

Measures
The circumradius R ≈ 0.58000 of the great inverted retrosnub icosidodecahedron with unit edge length is the smallest positive real root of:
 * $$4096x^{12}-27648x^{10}+47104x^8-35776x^6+13872x^4-2696x^2+209.$$

Its volume V ≈ 1.03760 is given by the smallest positive real root of:
 * $$\begin{align}&2176782336x^{12}-3195335070720x^{10}+162223191936000x^8+1030526618040000x^6\\

{} &+6152923794150000x^4-182124351550575000x^2+187445810737515625.\end{align}$$ These same polynomials define the circumradii and volumes of the snub dodecahedron, the great snub icosidodecahedron, and the great inverted snub icosidodecahedron.

Related polyhedra
The great diretrosnub icosidodecahedron is a uniform polyhedron compound composed of the 2 opposite chiral forms of the great inverted retrosnub icosidodecahedron.