Geology peacocks all its feathers with polished marble. If the discipline of graining is like playing Bach, then marbling is playing Coltrane jazz. More chemistry than craft one has to imagine semi molten rock, solidifying, cracking and maybe melting again. It's a 3d world.
Go into any European palace or cathedral and real marble goes up to 10ft... above that is plaster and paint. The reason you never noticed this is because highly skilled artists never let you see the join.