Small icosicosahedron

The Small icosicosahedron, se, or compound of ten octahedra is a uniform polyhedron compound. It consists of 40 triangles which form 20 coplanar pairs, combining into hexagrams. 4 triangles join at each vertex.

This compound is sometimes considered to be regular, but it is not flag-transitive, despite the fact it is vertex, edge, and face-transitive.

Vertex coordinates
The vertices of a small icosicosahedron of edge length 1 are given by all permutations of: Plus all even permutations of:
 * (±$\sqrt{2}$/2, 0, 0)
 * (±$\sqrt{6}$/4, ±($\sqrt{2}$+$\sqrt{2}$)/8, ±($\sqrt{2}$–$\sqrt{2}$)/8)