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How to Check Gold Purity?

Buying gold in any form can seem to be an easy and normal task. But with less information about the gold you are purchasing, the deal may end up being a worthless one. After all, buying gold isn't a child's play. However, it isn't that tough job either. You just need to make sure you are purchasing something real and valuable. So, how do you make sure if the gold that you are about to buy or have already bought is pure?

 Before buying any gold jewellery or gold coins, there is a simple way to check its purity. To certify the purity of gold that you purchase from genuine stores or online platforms, a government authority called the Bureau of Indian Standards (BIS), goes through a process of marking every gold piece with some information. This information, called the Hallmark, certifies the purity of gold. As per BIS, the process of hallmarking is done to protect the public against contamination and also to necessitate gold manufacturers to maintain legal standards of fineness and purity.

 According to BIS, there are four components to look on the hallmarked gold jewellery to ensure the purity of gold:

  1.  The standard BIS Logo/Mark
  2. Purity in Karat and fineness
  3. The Assaying and Hallmarking Centre's logo/number
  4. The Jeweller's own logo/mark/number

 Note: Before 1st January 2017, Gold Hallmarks also included the year of marking which was denoted by a code letter, e.g. 'A' for the year 2000, 'B' for the year 2001, 'R' for the year 2013 and so on. 

  1. BIS Logo/Hallmark

Any BIS hallmarked gold jewellery piece will have the BIS logo indicating that its purity is verified in one of the licensed labs of BIS. This logo will be familiar with every jewellery or coin you buy. BIS is the only government-approved agency in India for hallmarking gold items of any kind to ensure its purity.

 However, this hallmarking process is voluntary, and not all jewellers offer BIS hallmarked jewellery. Some of the local ones still offer their in-house hallmarking on their jewellery which is not verified by the BIS. Therefore, before buying gold jewellery from anywhere, you must make sure to check the gold piece for a BIS logo.

  1. Purity in Karat and Fineness

The second mark certifies the amount of gold purity in that jewellery indicated in two ways: Karat (denoted as KT or K) and fineness number. As 24K gold is too soft and bendable, gold alloys with other metals such as silver and zinc are used to produce a durable form of gold for making jewellery. According to BIS, gold hallmarking is done only for three levels of karats effective from January 1, 2017 - 22K gold, 18K gold & 14K gold. Before that, hallmarking was done for more levels such as 23K, 21K, 17K, 9K.

Fineness number is another way to measure the purity of gold in jewellery, measured in purity in parts per thousand. In simple terms, it is another name of 22K gold. For, e.g., if 22K gold weighs 100 gm, it contains 91.6 gm of pure gold per 100 grams of alloy.

 To understand these markings more clearly, here is a simple gold purity chart:

Markings Karat Pure Gold% Other Metals%
22K916 22k 91.6% 8.4%
18K750 18k 75% 25%
14K585 14k 58.5% 41.5%
The karat and fineness number on the surface of your jewellery piece indicates that BIS has certified it to be of the fineness level/purity that is embossed on it as part of the hallmark.

  1. Assaying and Hallmarking Centre's Mark

The third mark on the jewellery piece is the logo of the laboratory where that gold is assessed to check its purity. Only licensed laboratories of BIS are allowed to check the purity and put their mark. You can check on the BIS website if a particular hallmarking centre is licensed by them or not. 

  1. Jeweller's identification Mark

The jewellery store or online platform from where you purchase your gold jewellery also puts its identification mark or logo on it. This mark can be of a BIS certified jeweller or jewellery manufacturer.

The official BIS website has a list of jewellers that are certified by them.

 Test Purity of Gold Jewellery at Home using a Testing Kit

You can also test the purity of your gold piece at home using a gold testing kit. This kit is available for anyone to buy, and the principle is generally the same as that of professional karat testing. 

The kit generally contains several bottles with nitric acid of varying concentration and each bottle is labelled with a karat number, for example, "10K" or "14K".

 This is how most gold testing kits for testing at home usually work:

  •  First step is to rub your gold ring, or other gold pieces, on the testing stone that comes inside the kit. The item will leave a golden mark on the stone's surface.
  • Then by putting little drops of acid on that golden mark from the bottles provided, you need to look carefully for a colour change. 
  • Start by pouring from the bottle having the lowest karat number labelled on it.
  • If the colour of that mark changes significantly or disappears slowly, then the karat of the gold piece is less than the karat number on the bottle's label.
  •  If the colour changes only slightly, then it has the same or nearly the same karat as what the name on the bottle refers. (Here, about +/-1 karat of accuracy can be expected.)

And lastly, if the colour of the mark does not change at all, then the gold in your piece is of higher karat than the number labelled on the bottle. This means that next, you need to try a bottle with the next higher karat number.

It is suggested to start with the bottle that has the lowest karat number available in the kit and keep repeating the process until you get zero on the actual karat of your piece.

 Most gold testing kits that use nitric acid, function with this fundamental principle, although certain instructions or details may differ. But it is very essential to always read the instructions that come with the gold testing kits in detail before starting the test. If you don't want to use a testing kit, then there are other ways as well to test the purity of your gold piece. Read our guide on Identifying Fake Gold Jewellery to know more.

Check out the current gold rate online if you are planning to invest in gold.