I've been asked this question a few times, and while I *think* I know the answer, I'd like to know more.

Graphite, as we know, is a sheet polymer. Since polymers are bound to be finite by physical considerations, graphite must have "edges". My question is, what happens at these edges? 

I can cook up these possibilities:

* A graphene sheet "folds back" on itself, thus forming a tube and taking care of *most* of the edge carbons. But this would make graphite less slippery, so I doubt this is the case.
* Random elements/compounds from the environment at time of synthesis latch on to the edges, taking care of the valency of Carbon
* The edge carbons form double/triple bonds amongst themselves

I'd like to know more about this. I'm also curious what happens to the resonance of graphene at the edges.