Bullionism

Bullionism is an economic theory that defines wealth by the amount of precious metals owned. Bullionism is an early or primitive form of mercantilism. It was derived, in the 16th century, from the observation that the English state possessed large amounts of gold and silver, in spite of the fact that there was no mining of precious metals on English soil, because of its large trade surplus.
According to Adam Smith in his treatise, Wealth of Nations, goods and services are the real wealth of a country.

Gold and silver are mediums of exchange still subject to supply and demand.
When the Spanish Empire exported greater amounts of silver from their colonies to Spain, prices increased due to inflation of the currency.

The true power of a currency is its acceptance according to Thomas Sowell through his book, Basic Economics.