Gold Purity and Colour Guide: What is the difference between 24k, 22k and 18k gold

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Gold Purity and Colour Guide: What is the difference between 24k, 22k and 18k gold

The Different Karats of Gold

Karat is the term used to measure the gold content or purity. Before we understand the difference between 24k, 22k and 18k gold, you must know what karat stands for. Karat is basically a unit used to measure the purity of gold. The higher the karatage, the purer the gold. Here’s a simple guide to understanding the difference between 24k, 22k and 18k gold.

24K gold

24k gold is also called pure gold or 100 per cent gold. This means that all 24 parts in the gold are all pure gold without traces of any other metals. It is known to be 99.9 per cent pure and takes on a distinct bright yellow color. There is no higher form of gold than 24K and you must be aware of this before you go to a dealer who might tell you that they’re selling you 25K or 26K gold. Since this is the purest form of gold, it is naturally more expensive than 22K or 18K gold. However, this type of gold is lesser in density as compared to gold of a lower karatage which makes it soft and pliable. Hence, it is not suited for regular forms of jewellery. Coins and bars are mostly bought of 24K gold purity. 24K gold is also used in electronics and medical devices such as those used for children suffering from ear infections who are fitted with gold tympanostomy tubes that are known to improve aeration of the middle ear.

22K gold

22K gold jewellery implies that 22 parts of the jewellery amounts to gold and the balance 2 parts are some other metals. This kind of gold is commonly used in jewellery making. In 22K gold, of the 100 per cent, only 91.67 per cent is pure gold. The other 8.33 per cent comprises metals like silver, zinc, nickel and other alloys. It is this addition of metals that make the texture of gold harder thereby making the jewellery durable. However, you must know that although this can be used to make plain gold jewellery, 22K gold isn’t preferable for diamonds and heavily studded jewellery.

18K gold

18K gold is 75 per cent gold mixed with 25 per cent of other metals like copper or silver etc. Usually studded jewellery and other diamond jewellery is made in 18K gold. This kind of gold is less expensive compared to 24K and 22K. This one has a slightly dull gold colour. Recognizing 18K jewellery is rather simple – you will see the item stamped with 18K, 18Kt, 18k or a variation similar to these. At times, 18K gold is marked by 750, 0.75 or a stamp similar to these in order to symbolise that the jewellery contains 75 per cent gold.

How is fineness calculated?

In the West the karat is expressed in fineness. For e.g. 24 k gold is expressed as 1000 parts out of 1000 pure or fineness 1.000. 22 k is expressed as 22 divided by 24, multiplied by 1000 which will give you a fineness of 0.9166, 21 karat is 21 divided by 24 multiplied by 1000 which is 0.875 fineness and similarly 18 karat is 0.750 fineness.

The Different colours of gold

24 karat gold has the natural warm colour of pure gold and its colour cannot be changed without changing the purity to less than 24 k. Other colours of gold can be made by changing the composition of the alloy in the making of the jewellery.

  • Pink or Rose gold - Pink gold is made by adding more copper in the alloy composition of the gold
  • Green Gold – Gold is given a green colour by adding more of zinc and silver
  • White Gold – the white colour of gold is achieved by adding nickel or palladium
A surface colour can also be given to gold articles by electro-plating. However this can only be a surface finish and will be worn off over a period of time.

24 karat gold contains 24 parts pure gold. 22 karat gold contains 22 parts gold and 2 parts of other metals added as alloy. 21 karat gold contains 21 parts gold with three parts of other metals added. 18 karat gold contains 18 parts pure gold with 6 parts of other metals added. In the West the karat is expressed in fineness. For eg. 24 k gold is expressed as 1000 parts out of 1000 pure or fineness 1.000. 22 k is expressed as 22 divided by 24 , multiplied by 1000 which will give you a fineness of .9166, 21 karat is 21 divided by 24 multiplied by 1000 which is .875 fineness and similarly 18 karat is .750 fineness.

Buyer's Tip

24 karat = 99.5% pure gold and above
22 karat = 91.7 % gold
18 karat = 75.0 % gold
14 karat = 58.3 % gold
12 karat = 50.0 % gold
10 karat = 41.7 % gold

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Bullion includes precious metals in the form of bars of minimum 99.5% purity.

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