Quote Originally Posted by Omegas View Post
On the other hand everyone exchanges gold. There is always the possibility of trade but if I walk into a Burger King I am going to have a hard time trading a gallon of gas for a burger.
This is why currency was invented, to add a layer of abstraction to transactions. It works extremely well for the purpose, as we can see whenever someone who works at Burger King uses dollars from their paycheck to buy gas at Shell for exactly the same price as anyone else, or vice versa.

There is no particular reason to suppose that Spirit Sand would be any different here: it has supply, and it has demand, and it is not especially tied to any one person's use, so it's certainly something that can be traded; it even has a fairly stable value. This makes for an excellent trade good, or in other words, something that can always be exchanged for very nearly the same amount of gold or other valuable.