According to the Bureau of Indian Standards (BIS), hallmarking is the accurate determination and official recording of the proportionate content of precious metal (gold or silver) in articles. It ensures 92 per cent purity of gold ornaments. Hallmarks are, thus, official marks used in many countries as a guarantee of purity or fineness of precious metal articles.

Jewellery hallmarking provides a third-party assurance — that a buyer is getting the right purity of gold or silver jewellery for the given price. Many buyers get their jewellery re-checked by a third party — BIS — to confirm the purity of the piece. Now, the hallmark will be a certification for such individuals." Many jewellers like Gitanjali Gems, Tanishq and Waman Hari Pethe already provide hallmarked jewellery. In 2007, hallmarking was made mandatory in four metro cities. "Last time," says Mehul Choksi, CMD of Gitanjali Gems, "it got deferred for other cities because not everyone had the right infrastructure to hallmark jewellery. This time they will make it mandatory for jewellers across the country." Importantly, lack of proper infrastructure has made hallmarking expensive in India. This, in turn, pushes up your cost of jewellery — both readymade and customised ones.

Hallmarked jewellery also helps when you need to sell or exchange jewellery. Jewellery buyers are often told the piece of jewellery being bought is 22 carat. Only when selling or exchanging does the individual discover the jewellery piece was only 18 carat. Many lose money this way. Industry experts say this problem also arose due to the lack of suitable solders for high-carat jewellery, preferred in India. Higher the caratage, softer the metal, and it can bend or break easily. Such jewellery needs soldering and the solder alloys used are of a much lower caratage, leading to undercarating.

Then, there is adulteration by addition of too much alloy and selling gold or silver-coated articles with base metal cores. These frauds still continue at least in the local jewellery market.

If you have not bought from the jeweller whom you approach for selling/exchanging, he will weigh the caratage, tally it with the hallmark and pay according to the weight. There are chances the weight then varies slightly from that when you had bought the jewellery, especially if you've worn it regularly.

Old jewellery can also be hallmarked. This is advisable if you are giftingl.

You will have to approach aBIS-recognised assaying and hallmarking centre to get it done. At the centre, the jewellery will be checked for caratage and hallmarked accordingly.

This, even if you were told a different purity when you had bought it.

BIS-recognised assaying and hallmarking centres charge for hallmarking. It differs from piece to piece and according to weight.

"BIS-recognised centres have been advised to charge for gold ~18 an article and a minimum charge for a consignment shall be ~100," according to a BIS statement.

But, jewellers may charge you based on the type and weight of the jewellery.