When people buy gold jewelry in the store, the seller often describes it in terms of karats (abbreviated kt or K). The gold jewelries are made with different karat, such as 10 karat, 12 karat, 14 karat, and 18 karat. High karat gold jewelries are more expensive. Well, what exactly does the "karat" mean?
Karat is a unit of purity for gold alloys, rather than weight. The word "karat" is from the carob seed, which was used as balance scales to measure the weight of gold in ancient Asian bazaars.
Since the pure gold is too soft to make exquisite jewelries. Therefore, the gold jewelries are almost alloy which are mixed with other metals, such as silver, copper, or zinc. Pure gold is 24 karats. A unit karat of gold is equal to 1/24 part (4.1667%). The gold karat shows how many parts of gold and how many parts of other metals in a gold jewelry. The following chart shows the differences between the different karats, and also shows the percentage of gold and other metals.
|Karats||gold percentage||Other Metal percentage|
|24kt||gold 100.00%||other metal 0.000%|
|22kt||gold 91.60%||other metal 8.4%|
|18kt||gold 75.00%||other metal 25%|
|14kt||gold 58.5%||other metal 41.500%|
|10kt||gold 41.7%||other metal 58.300%|
|6kt||gold 25%||other metal 75%|
As I mentioned, gold is a relatively soft metal, so high-karat stuff are often easily damaged. A 24 karat item is generally reserved for display or ceremonial use. In the stores, most gold items have a karat rating in the range 9 to 18. In the US, the minimum karat value for gold jewelry to be sold is 10, but in the UK 9 karat is more common. In additional, gold purity does not affect its weight! Different color of gold are mixed with different other metals. For example, gold mixes copper is called red karat gold.
We are often confusion over the differing use of "carat" and "karat". The Karat is a gold unit for purity, and Carat is a unit for mass which is used for measuring the weight of gemstones and pearls (1 carat is equal to 200mg). However, carat and karat are usually used interchangeably in some countries.
There are two common methods to test gold for its purity, Acid Test Kits and Electronic Testing Kits. However, any acid testing will lose some small amount of gold.