Hi Tom,

Re: Terminology.

Icosahedra (plural), are solids with twenty planar faces. There are an infinite number.

The regular icosahedron has equilateral triangular faces.

Polyhedra have various numbers of faces.

- Brian

In the past, I have used MoI to manually build the platonic solids, as an exercise.

There was a file with a lot of "gem" solids...
Also, antiprism script.