Granite router/mill

(Not the Smithy Granite)

I'm wondering about the feasibility of building a router/mill out of
granite. Specifically, cheap surface plates. They have a lot of mass,
are inexpensive, and are flat and square, seems ideal. Use one for the
bed, two for uprights, and one for the cross member of the gantry. I
wonder how you would attach them together, and how you would attach
roundways and the like to them?

Comments appreciated.

Regards,
JJ