bitGold and bitSilver exist. They are smartcoins that are pegged to the price of their respective metal. Each smart coin is backed by 1.75X the equivalent value in bitshares that are locked in a smart contract. There is also a deal in the works with the United Precious Metals Association to make a bitshares bitAsset pegged to the value of gold and actually redeemable in real physical gold. Good times ahead! Cheers!