Karat: Gold Purity Calculation Guide

Gold content or purity is measured by Karat and it is basically a unit used to measure the purity of gold. That means the higher the karatage, the purer the gold.

Types of Karat are-

a) 24K

b) 22K

c) 18K etc.

a) 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 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.

b) 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.

c) 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.

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 gold for example is made by adding more copper in the alloy composition of the gold.
• Green gold is more of zinc and silver and white gold is more of nickel.
• 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.

Fineness calculation of gold- In the West the karat is expressed in fineness. For example

• 24 karat gold contains 24 parts pure gold & it is expressed as 1000 parts out of 1000 pure or fineness 1.000.
• 22 karat gold contains 22 parts gold and 2 parts of other metals added as alloy& it is expressed as 22 divided by 24 , multiplied by 1000 which will give you a fineness of 0.9166.
• 21 karat gold contains 21 parts gold with three parts of other metals added & it is 21 divided by 24 multiplied by 1000 which is 0.875 fineness.
• 18 karat gold contains 18 parts pure gold with 6 parts of other metals added & it is 0.750 fineness.

Purity Chart_

• 24 karat = 100%   gold or Pure gold
• 22 karat = 91.7%  gold or Pure gold
• 18 karat = 75.0%  gold or Pure gold
• 14 karat = 58.3%  gold or Pure gold
• 12 karat = 50.0%  gold or Pure gold
• 10 karat = 41.7 % gold or Pure gold