From Forbes Magazine: Even US banks now consider gold to be a currency:

JP Morgan Accepts Gold As Collateral For Stock Purchases

Comes the revolution!. You can use your non-income producing gold as a way to buy other securities yielding some income return or as a way to post money with counter-parties.

This means gold holdings of hedge funds or wealthy investors will be treated as the equivalent of treasury bonds or other securities that can be used to leverage other investments. Another imprimatur for gold being treated as a normal credit substitute in financial markets.