Brass, copper, and steel might become common currency, with something on the order of the British shilling, might also become more common. Like a coin worth a pound of sterling silver. There are still countries whose banking uses the silver as a standard, instead of gold, and even something like a Krugerrand might make a better substitute, if you use it like the sterling coins.
Since gold is heavier, it can be used in varying sizes to represent varying weights of silver, or even copper, instead. Copper pennies and brass pennies might also be considered, and electrum might be used in some cases.
The United States even had a steel penny during WWII, because certain substances became scarce (like copper).
Give that some thought. If Gold is in different quantity, then Tungsten might be used, with copper and brass supporting it, and gold minting dropped altogether.