From Fertile to Infertile Media of Payment
To achieve monopolistic control over a medium of payment one has to control its quantity by preventing others from creating it.
The reference goods mentioned before have a couple of interesting features more: they are food, something highly and directly valuable, and they are fertile. A cow, a sheep, a grain of wheat produce more cows, sheep, grains of wheat.
Now look at gold: can it procreate more gold?
If a medium of payment is not fertile, the authority to produce it will be a power, sought after and disputed.