Asked Google, got this thread!

I'm planning (or set on) picking up some cheap granite / quartz worktop for work-bench tops. I wondered just how flat it tends to be, but perhaps that is a question about how long is a piece of string? Is granite and quartz different in this regard? I imagine a man-made material will be flatter than a cut true stone and what they call quartz seems in fact resin based.

Anyway, perhaps I can do a rough check for high and low spots by lapping? I have a 400mm x 400mm slab of 15mm cast ali tooling plate (faced both sides at factory) so I guess that would surface as good beginners lapping plate and give me an idea of my worktop flatness?