The United States Mint, concerned that rising metal prices could lead to widespread recycling of pennies and nickels, has banned melting or exporting them.

The Mint is also testing dozens of cheaper alternative metal compositions in the expectation that Congress will mandate a change when it meets in the new year.

According to calculations by the Mint, the metal value of pennies, which are made of copper-coated zinc, is now more than one cent. The metal value of 5-cent coins, made from a copper-nickel blend, is up to 7 cents. Adding in the costs of manufacturing means the Mint now spends 1.73 cents for every penny and 8.74 cents for every nickel it makes.

Until 1982, pennies were made of 95 percent copper. The commodity metal value of one of those coins, which still make up a large percentage of the pennies in circulation, is 2.13 cents, according to the Mint.