A little clarification is in order I think. I am a stone mason. I have been fabricating and installing 2 and 3 centimeter granite slabs for homes and businesses for many years (kitchen counter tops especially.) I will soon have access to a CNC machine which I will use to drill holes, cut miter and t-track slots, cut out edged holes for plates and chamfer the edges (although I am thinking of epoxying a hardwood edge on all around.) Aquiring the material is not a problem (we generate, literally, tons of scrap.)
Attaching the stone is not a problem either. I could use t-bolts underneath. This would make it removable. But I think I will use epoxy to laminate it to a sub-top. It can be attached to any moble or fixed base.
Granite is harder than steel. It can only be cut with diamond tools. It is very dense so it will have a dampening effect on vibrations. Like cast iron, it can be machined very flat. It can be polished to a high shine, but for a work top it is better to be honed to a matt finish. I have made a face frame clamping table of polished absolute black granite by surrounding it with 80/20 t-track. It has been great. Just take a razor blade to scrape off any glue.
My question really wasn't should I make a granite router table top. It was has anyone in the community done it.
It will be a while before I get the top plotted for the cnc and there may be a "trial and error" period. When I get one, though, I will share the cnc program with everyone. That way someone could take the program to a cnc equiped fabrication shop and say "Here, make this out of a piece of your scrap, please."