Said stone was the five elemental infusion stone, a stone that contained the fusion of all the five elements and unlike the other stones, this one was considered a dao natural treasure because of the effects it had.
The five elemental infusion stone could be used to polish the body of a cultivator giving them at the bare minimum a gold body in the body refinement stage, and when breaking through to the foundation establishment realm provided they used the stone to polish their foundations in the previous two realms, they were guaranteed at the very least to have blue grade pillars regardless what grade of cultivation art they practiced.