The purity of gold is measured in karats. Pure gold measures 24 karats but is too soft in this state to be used effectively in jewelry. That’s why gold is alloyed with other metals (such as silver, copper, nickel, and zinc) to increase its strength and durability. Common measurements (once the alloy is added) are 18 karat (75% gold), 14 karat (58%), and 10 karat (47.7%). In the United States, the legal karat limit for the metal to still be considered gold is 10 karats. A higher karat measurement in gold content indicates a greater value of the jewelry piece. Gold jewelry should always be stamped with the karat mark, either 18k, 750 (European marking for 18k), 14k, 585 (European marking for 14k), or 10k. In addition, to assure its quality, the piece should be stamped with the manufacturer’s trademark or country of origin.
Pure silver is soft and easily damaged. To give it more durability when creating jewelry, it is combined with copper, which makes it sterling silver. Sterling silver is 92.5% silver and 7.5% copper, but this alloy does not have an effect on the value of the metal. To ensure that the silver is high quality, jewelry should be stamped with a quality mark. According to federal law, the mark must be accompanied by a registered trademark or maker’s mark. Acceptable marks for silver include: sterling, sterling silver, ster, .925.
Platinum is the most durable of fine jewelry metals. It does not chip or splinter easily, making it perfect for diamond and gemstone settings. Platinum jewelry is usually 95% pure platinum with 5% iridium or palladium alloy. It can also be 90% pure platinum with 10% iridium or palladium alloy. To guarantee its quality, each piece should be stamped with a 900 Plat to denote 90% platinum or a 950 Plat or Plat mark to denote 95% platinum. If platinum becomes scratched or a patina begins to develop, a jeweler can restore the original shine.