How are granite countertops cut?
 

I have some rental properties and thought it might be a good idea to instal something that tenants would have a hard time to destroy, LOL

I could buy granite countertops at auction at a steal of a deal in 7'6" lengths (fronts already finished) but I would really need to add another 4' which means they need to be cut. Is this possible as a DIY project? I am familiar with a wet saw but this is different than tile of course. Any ideas?

Clamp a straight edge on it, cut it with a diamond blade in a skil saw. Keep a little water on the surface for the dust.