Why does my cat bring home and/or eat charcoal?

My cat is only about 13 months old, he's a Maine Coon, and he brings home pieces of wood charcoal. We aren't certain he is eating it since we just see him bring it to the door and he has black on his teeth and lips like an oreo. He doesn't hunt very well, only finds little critters and watches them or follows them around. (he's kind of dumb) Any ideas?