My personal opinion, being as you are going for the rustic look,
one of three options:
1 - real butcher block
2 - slate
3 - concrete with slate tinting
The problem is these require maintenance and care to last long.
Personally, I hate when people put granite into
a house that is supposed to be rustic.
We have an old house tour every year in Berks county
and the slate just looks out of place in some of teh houses.
Here's a link to the yearly tour:
http://www.berkshistory.org/events/3cent.html