You know, I'm not really sure but am ok with that.. Anyway my thoughts would be that this substance, if formed, would initially be of a Universal nature, thus having the ability to transform all Kingdoms. So precious metals only forming under proper circumstances. Other forms of change occuring depending on the variables of the specific instances in question. Maybe all things Evoulutions owe their transformation to such a contact with a not yet Fixed Stone-like substance that forms naturally.

No one really seems to know these things for sure.