When making jewelry, gold is mixed with other metals to strengthen the piece and create more durable jewelry. We use the term, karats, to specify the amount of gold in the jewelry. A higher karat means higher gold content, higher purity and higher value. Karat can also be spelled with a C in other countries (carat).
Gold jewelry is often stamped with either the karat (K) or the millesimal fineness gold hallmark to indicate its gold content. Usually the marking also has a trademark near it that identifies its maker. The country of origin can also be included.
Karat purity is measured as 24 times the purity by mass.
|24 Karat Gold Jewelry||99.9%||24 of the 24 parts are gold.||999|
|22 Karat Gold Jewelry||91.7%||22 of the 24 parts are gold and 2 parts are one or more other metals||917|
|18 Karat Gold Jewelry||75%||18 of the 24 parts are gold and 6||750|
|14 Karat Gold Jewelry||58.5%||14 of the 24 parts are gold and 10||585|
|12 Karat Gold Jewelry||50%||12 of the 24 parts are gold and 12||500|
|10 Karat Gold Jewelry *||41.7%||10 of the 24 parts are gold and 14||417|
|9 Karat Gold Jewelry||37.5%||9 of the 24 parts are gold and 15||375|
*10 karat gold is the minimum purity to be considered gold in the United States.
24 karat gold jewellery is not very common because 24 karat gold is soft and not very durable for jewelry. Mixing other metals to create a gold alloy adds strength to gold jewelry, so it is more scratch resistant and will not be damaged as easily as 24 karat gold jewelry. Alloys can also be mixed to create different colors of gold, such as green gold , red gold and even white gold.
Most gold jewelry is 18 karats or less; however, there are 24 karat gold and 22 karat gold jewelry pieces that are worn for ceremonial occasions and bought as investment pieces. Because of their high gold content and the designer’s prestige, such pieces rarely lose value and can increase in value if the designer becomes famous or dies.
There are x-ray fluorescence instruments that can test the purity of precious metals and jewelry. These machines can measure gold content without damaging fine jewelry and can even determine the composition of gold jewelry, such as gold, silver, platinum, paladium, rhodium and other alloys.