The pyritohedron:
These crystals have pairs of faces with striations running the same way.
The two faces on the left show the pattern.

The face on the right has its partner face extending around the back edge and is part of a horizontal pair.
Two corresponding pairs are on the back.

There is a pair on the top and another on the bottom.

In all, there are six pairs corresponding to the six faces of a cube.

Specimen is 1 1/8 x 1"