ua549's link provides an excellent portrait of a Black Belt project. It is a full spectrum.
The experience I have reflects that list. In addition, I'd like to emphasis on the dollars that you have to prove that you can save through that BL project.
If your project can improve a lot of things, but does not cut much cost, then it is not a BL one.
Also, most of the BL projects I have seen concentrate on business processes.
I know that, have been trying to identify one for myself. To tell you the truth .. hard to find.
Good luck!
ISOTO