Polyhedra
Polyhedra can be inserted into a document by using the extrenal Pyramids and Polyhedra Workbench Polyhedra.
The Workbench can be installed, as usual, using the FreeCAD Addon Manager.
An example screenshot showing four different types of polyhedra
as they appear in the FreeCAD document (left) and
as displayed in the load_gdml_color application (right) is shown below.
The FreeCAD file can be downloaded from here Polyhedra