http://www.potsaa.com/stoneware-plate/

Is a sandstone slab intended to be uneven?
I just ordered and received the sandstone slabs. The wheels – the whole band on the edge plate – are higher on one side of the plate than the other. Kind of wavy. Is this normal for the sandstone, or should I send as defective? I have not noticed this on the bowls, which have not broken rims. Our older sandstone is uneven, but I attributed this to the fact that it is a cheap brand. The new set is a better brand, so I do not know whether to expect that uneven border or not.
you should return the sandstone tiles, sandstone should becompletely flat on all sides, certainly not wavy
Throwing a plate – Allen Stoneware Gallery