Traditional metals used in jewelry are the “noble metals”: silver, gold and the platinum metal group (including platinum and palladium). Noble metals are so called because of their ability to withstand corrosion and oxidation and their chemical stability. Today's jewelry is more varied and versatile than ever. This is partly due to the use of new types of metals and alloys used to make jewelry.
Through the use of alloys, two or more metals or elements can be combined to give the resulting metallic substance certain properties that are different from its component metals. The primary purpose of alloys in jewelry is to give metals more desirable characteristics. For example, pure gold (24 karat gold) is too soft for prolonged wearing and would scratch easily. Most gold jewelry is either 14 karat gold or 18 karat gold which consists of gold mixed with other alloys, usually silver, nickel, copper or zinc. Sterling silver is silver mixed with alloys to make it stronger. Sterling silver is 92.5% pure silver usually mixed with 7.5% copper.