Pentagonal dipyramid

In geometry, the pentagonal dipyramid (or bipyramid) is third of the infinite set of face-transitive dipyramids.

The set of dipyramids is the dual of the uniform prisms.

It is also a Johnson solid (J13), constructed of regular polygons. It can be seen as two pentagonal pyramids (J2) connected along their bases.

As a Johnson solid, it is a convex deltahedron. Although it is face-transitive, it is not a Platonic solid because some vertices have four faces meeting and others have five faces.

The Johnson solid 13 is made of 10 equilateral triangles.