Gold jewelry is marked with a stamp to indicate its purity. Symbols indicating the purity of gold include carats, or karats, and a system of numbers that represent the percentage of gold to other metals.
Gold, with the chemical symbol Au, is one of the most popular precious metals used in the manufacture of jewelry, coinage and decorative items. Gold is found in veins in rock or loose as nuggets.
Pure gold is bright yellow, soft, shiny and malleable. For jewelry production, it is mixed with other metals, in varying proportions, to add strength. The amount of other metals in proportion to pure gold is indicated with numbers, like 916, or karats, ranging from 24 to 10.
Carats or Numbers
In the West, pure gold is rated 24 karat. It is marked "24kt." In India, and some other countries, the highest purity of gold is 22 karat, or 916, which means 91.6% pure gold and 8.4% silver and other metal alloys like copper.
The Kadmium in KDM
Some gold jewelry is marked 916 KDM. This is 22 karat gold combined with cadmium, or kadmium, alloy. Before some countries banned the use of cadmium, which produces toxic fumes at very high temperatures, cadmium was used for soldering gold jewelry. Cadmium is safe in finished jewelry, but dangerous during the manufacture process.
The purer the gold, the more expensive the gold. Gold that is a high Karat, like 24kt or 22kt, is more expensive than 14kt. Gold marked 916 is 22kt gold, and priced at that level.
Gold of all karats or percentages comes in a variety of colors, including yellow, white or rose, created by the type of alloy used in the manufacture process. The pure gold content is measured the same way in all colors of gold. Yellow gold that is 916 will be the same purity as white gold that is 916.