I was pondering what would happen if somebody launched a completely separate Bitcoin clone except they tweaked the code slightly so the Bitcoin clone could be backed by gold. Below I discuss Goldcoin, a hypothetical Bitcoin clone except backed by gold, where goldcoins would have all the properties of bitcoins except each goldcoin would be redeemable for a predetermined amount of gold.
You don't need a separate currency since you can just create a company that will sell gold for bitcoins.