Gold is listed as a commodity in the WSJ, it's an asset, not a currency. Not many central banks have gold vaults anymore, most have sold their gold for more useful, liquid assets like US Treasurys.
The definition of a currency......
What is 'Currency'
Currency is a generally accepted form of money, including coins and paper notes, which is issued by a government and circulated within an economy. Used as a medium of exchange for goods and services, currency is the basis for trade.