"Karat" Defined

Look for the quality mark. Pure gold, or 24-karat, is generally considered too soft for use in jewelry, so it is alloyed with other metals to increase its strength.

Eighteen-karat gold is 18/24ths, or three-quarters pure gold. Jewelry of this fineness is marked "18k" or "750," the European designation meaning 75 percent gold.

In the United States, 14-karat gold is used most commonly for jewelry. Fourteen-karat gold is 14/24ths, or slightly more than one-half pure gold. Jewelry of this fineness is marked "14k" or "585," the European designation meaning 58.5 percent gold.

Nothing less than 10-karat gold can be legally marked or sold as gold jewelry in the United States. These pieces are marked "10k" or "417," the European designation meaning 41.7 percent gold.