Cutting on marble/granite slab bed?

I’m curious - what happens to marble/granite when you CUT on it ?
I know about the engraving minerals thing, but what about using it as super-flat bed ?
What if i went in with 100w at 10mm per sec at a chunk of polished granite ?

Still waiting on my steel flat bed to be cut for me, but might get a hold of a big chunk of granite kitchen top to act as a flat bed ? Good idea ? Bad idea ?

Bad Idea:

I think you would get a lot of reflection, reduced air assist, and undesirable heat on the bottom of material.

Get yourself a honeycomb bed.

Its the honeycomb that i try to get rid of. Wavy/sloppy/saggy mess and a nightmare to focus on. Cant use whole bed because of that.

I’m not talking about cutting straight on the granite, use some sort of lifting jig, standoffs etc. I think granite would make very good and stable bed that if propely leveled is best for focusing throughout the size of the bed. But then i wondered the effect of strong beam on granite, stronger than engraving runs, full-on cutting strength (it would be out of focus somewhat if material lifted by 5mm). Doesnt mineral material absorb most energy ? Its the metals are reflective to typical co2 radiation, no ?