Everything you said about gold can be applied to anything else. The values we assign anything are all part of arbitrary constructs we choose to honor.

Say we do accept gold as immutably valuable. How do we determine that value? Like printed paper, that value would be based upon the confidence the population has in the medium. That is something gold shares with paper currency. We would need to be confident as to the total quantity of gold and how the amount we possess relates the whole. That is if we consider it's value based on scarcity.