The thermal inertia $I$ of a material can be thought of as the materials tendency to absorb thermal energy. It is a combination of the thermal conductivity $k$ of the material and its volumetric heat capacity $ρc$
$$I=\sqrt{kρc}$$
Where $k$ = thermal conductivity
$ρ$= density
$c$= specific heat.
$ρc$= volumetric heat capacity
So to compare slabs of the same dimensions, particularly thickness, those slabs comprised of materials having the highest thermal inertia should should theoretically have the greater tendency to absorb heat.
I haven't found any tables for thermal inertia of stone materials, but here is a site that provides information on their thermal conductivity.
https://www.naturalstoneinstitute.org/stoneprofessionals/technical-bulletins/rvalue/
BTW if it were me I would use a granite counter top. Many folks have them. I use mine to help defrost things like frozen hamburger patties. Works great.
Hope this helps.