Karats (Carats outside of the United States, ) in gold jewelry refers to the amount of gold that is present in the jewelry piece. Europe describes the karatage of gold jewelry in ‘fineness’, which is the gold content expressed in parts per thousand.
The purer the gold content in a piece of jewelry, the more valuable it is. Gold is mixed with alloys, metals added to strengthen the gold to create more durable jewelry, particularly in gold rings and gold bracelets.
24 Karat gold is often refered to as 'fine gold'. 24 Karat gold is from 99.0% to 99.9% pure gold depending on a country's laws. In China, 24 Karat gold is called “Chuk Kam”, meaning ‘pure gold’ and has a gold minimum of 99.0%. According to the World Gold Council, in China, Hong Kong, and Taiwan, 24 carat(Karat) gold is the typical caratage (fineness)."
There is very little 24 karat gold jewellery sold in other parts of the world. 24 Karat gold is soft and not very durable for jewelry. Mixing other metals to create a gold alloy gives strength and hardness to gold jewelry. This means gold jewelry wears better, is less scratch resistant and will not be damaged or distort as readily as 24 Karat gold jewelry.
Mixing other metals with gold also gives a variety of coloured golds used in gold jewelry creation. Colours such as green gold , pale yellow gold , yellow gold, rose gold or pink gold to red gold, as well as white gold.
Most gold jewelry worn on a regular basis is 18 Karats or less for durability and cost. However, there are 24 Karat gold and 22 Karat gold jewelry created as special designer pieces that are worn for special occassions and bought as investment pieces due to their high gold content and designer's artistic prestige. Such pieces rarely lose their value and increase in value as a designer becomes more famous or passes away.
The different grades of karats are:
24 Karat Gold Jewelry, where 24 of the 24 parts are gold, 99.99% fine gold.
22 Karat Gold Jewelry, where 22 of the 24 parts are gold and 2 parts are one or more additional metals, making it 91.7% gold.
18 Karat Gold Jewelry, where 18 of the 24 parts are gold and 6 parts are one or more additional metals, making it 75% gold.
14 Karat Gold Jewelry, where 14 of the 24 parts are gold and 10 parts are one or more additional metals, making it 58.3% gold.
12 Karat Gold Jewelry, where 12 of the 24 parts are gold and 12 parts are one or more additional metals, making it 50% gold.
10 Karat Gold Jewelry, where 10 of the 24 parts are gold and 14 parts are one or more additional metals, making it 41.7% gold.
10 Karat gold is the minimum karat that can be called "gold" in the United States. Some other countries, such as Australia, sell 9 Karat gold jewelry as "gold" jewelry
9 Karat Gold Jewelry, where 9 of the 24 parts are gold and 15 parts are one or more additional metals, making it 37.5% gold.
European Gold Jewelry
European gold jewelry indicates the gold purity as a 3 digit number.
24 Karat Gold Jewelry is marked 999 to show a 99.9% gold purity.
22 Karat Gold Jewelry is marked 917 to show a 91.7% gold purity.
18 Karat Gold Jewelry is marked 750 to indicate 75% gold purity.
14 Karat Gold Jewelry is marked 585 for 58.5% gold purity.
12 Karat Gold Jewelry is marked 417 for 41.7% gold purity.
Gold Jewelry is stamped with the the Karat(K) or in Europe, a number such as 750 (75% gold purit, see above table) for 18K, to indicate its gold content. The Karat marking also has a hallmark or trademark near it that identifies its maker. Also the country of origin may be included.
There is X-ray fluorescence instrumentation available to test the karat measurement of precious metals and finished jewelry. These machines allow a karat gold measurement without damaging fine jewelry.Some can also accurately determine the element composition of gold jewelry including gold, platinum, silver, paladium, rhodium and related alloys.