Need a sign that demand for gold coins is surging in the troubled economic environment?

The U.S. government has helpfully provided one. Last month, Reuters reported that the U.S. Mint has run out of 2010 American Buffalo One Ounce Gold Coins.

The 24-karat coins are notable for containing an ounce of pure gold; this year, they've already gained more than 20 percent in value in terms of the bullion alone.

The coins were first minted in 2006, after Congress authorized the minting in 2005.

The Mint said that it won't restock the coins, so it's possible that the Buffalo gold coins will end up being a prized and sought-after collector's item.

While it's good news for the buyers who managed to snap the coinage up, it could be a sign of danger to come in the broader economy. Investors have a tendency to buy physical gold when times are bad, inflation seems imminent and fiat currencies are looking shaky.

Such strong demand for pure gold coins indicates that Americans' confidence in the economy is wavering.