First, the smell. With a match or lighter to burn small pieces of the sample, although high quality table will have a little bit of smell, but not obvious; and poor quality table will have a very pungent odor, worse you will be at risk of burning.
Second, check the hardness. Can carry on the small sample of hard objects (such as keys, knives, etc), good quality counter tops should be scratch easily and not obvious; and the poor quality of the table clearly can see traces of the scratches.
Third, the surface quality. Quality table plate front, cross section and back entirely consistent, and free of porosity, color (block) uniform smoothness and brightness is very high, while the lower-quality table may not live up to.