This shape works very nicely as a 12 sided die, providing an elegant alternative to the regular dodecahedron.
It's is a hexagonal dipyramid, an isohedron.
For more information on unique dice shapes, see http://loki3.com/poly/fair-dice.html.
1.616 w x
1.616 d x
0.636 w x
0.636 d x