Original: One of the forms , called the pyritohedron ( named for the group of minerals of which it is typical ) has twelve pentagonal faces , arranged in the same pattern as the faces of the regular dodecahedron .
Simplified: The dodecahedron ( 12 sides ) is combinatorially identical to the pyritohedron ( in that both have twelve pentagonal faces ) , which is one of the possible crystal structures of pyrite .