Gold quality is determined by karat content or fineness, and each karat is 1/24th part of the entire substance. Since gold alone is too soft to hold a form, gold is combined with other metals in order to make jewelry.

Pure gold is 24 karats (100% gold), and as it is alloyed with other metals, the gold content decreases. 18k gold is 18 parts pure gold and 6 parts of alloy metals (75% gold); 14k gold is 14 parts pure gold and 10 parts other metals.

When buying gold jewelry, always look for the karat mark or "k" that appears on the back of the jewelry. By U.S. law, if a karat mark appears you should also see the manufacturer's trademark to assure you that the karat marking is accurate. The country of origin should also appear.

The higher the karat, the more expensive the jewelry. In the United States, 14-karat gold is the most common degree of quality. Nothing less than 10 karats can legally be marked or sold as gold jewelry in the U.S. However, lower percentages, such as 8-karat gold are popular in other countries.