That would be a pretty big hole in the law
If you actually have to exchange "money" for money laundering. If you could exchange gold, diamonds, Ferraris, or something else that's not legal tender in the US and avoid money laundering charges, you'd think no one would ever be guilty of it.
After all, the end goal of money laundering is to take something of value received for illegal transactions that may link you to those transactions and replace them with something of value that won't link you to those transactions. All that is required is that you can exchange that "something of value" for something else you want. Sure, untraceable bales of $100 bills is best, but ownership certificates for a warehouse full of copper ingots in New Jersey or Beijing will serve the same purpose, as you'd be able to borrow money against it and use that money to buy Ferraris, beach houses and hookers, which are all a drug lord really wants in the end.