How to check gold purity at home: 5 simple tests to identify genuine gold jewellery; check BIS hallmark and HUID
With Dhanteras and Diwali approaching, gold purchases are picking up across India as consumers look to buy jewellery, coins and other precious metal products during the festive season. However, concerns over adulteration and gold purity remain important considerations for buyers.
Many consumers may not know how to distinguish genuine gold from jewellery containing a higher proportion of other metals. While professional laboratory testing remains the most reliable way to establish gold purity, certain simple checks at home can help identify possible irregularities.
Jewellery experts recommend checking the BIS hallmark and six-digit Hallmark Unique Identification (HUID) code before purchasing gold. Consumers can also use a few preliminary tests to assess the authenticity of their jewellery.
Here are five methods to check gold purity and understand how experts test the precious metal.
1. Check the BIS hallmark and six-digit HUID code
The BIS hallmark is one of the most important indicators of gold purity in India. Hallmarked gold jewellery carries three key identification marks: the BIS logo, the purity grade and a six-digit alphanumeric HUID code.
Consumers can use the BIS Care mobile application to verify the HUID number and obtain information about the jewellery’s declared purity, identification and registration details.
The app can help buyers establish whether the hallmark details correspond to the jewellery they have purchased.
Consumers who have bought gold from local jewellers in smaller towns or villages can also approach a BIS-recognised Assaying and Hallmarking Centre for purity testing. The stated testing charge is ₹236, although buyers should confirm the applicable fee with the centre.
Experts advise consumers to prefer HUID-marked jewellery and retain their purchase invoices. These documents can help them raise complaints if they discover discrepancies in quality or purity.
2. Use a magnet to check gold authenticity
Gold is a non-magnetic metal, making the magnet test a simple preliminary check.
Bring a strong magnet close to the jewellery and observe whether it is attracted to it. Genuine gold should not stick to the magnet.
If the jewellery is strongly attracted, it may contain magnetic metals such as iron or certain nickel alloys.
However, this test cannot conclusively establish gold purity because several other metals used in jewellery are also non-magnetic. Therefore, a lack of magnetic attraction does not guarantee that the jewellery is genuine.
3. Conduct the water test
Gold has a relatively high density compared with many commonly used metals.
For this test, fill a transparent glass or container with water and carefully place the jewellery inside. Genuine solid gold will sink because of its high density.
If the jewellery floats, it may indicate that it is hollow or made from a different material.
However, this method cannot reliably distinguish pure gold from gold alloys. Hollow jewellery and certain design features can also affect the result.
4. Vinegar test to check gold purity
Another commonly suggested home method involves applying a few drops of vinegar to the jewellery.
Gold is chemically resistant to ordinary vinegar, so pure gold generally does not react or change colour when exposed to it.
A visible colour change may indicate the presence of other reactive metals or a surface coating.
However, this is not a reliable purity test. Gold-plated jewellery may also show no immediate reaction. Consumers should avoid applying household chemicals to valuable jewellery because they may affect other materials, gemstones or surface finishes.
5. Ceramic scratch test
The ceramic test is another traditional method used to identify potentially fake gold.
In this method, jewellery is lightly rubbed against an unglazed ceramic surface. Genuine gold may leave a golden streak, while certain base metals can produce a dark or grey mark.
However, this method is potentially destructive and can scratch or damage jewellery. It should not be used on valuable ornaments, especially those with polished finishes or gemstones.
How is gold purity tested by experts?
Jewellers and authorised testing centres use specialised equipment and scientific methods to establish gold purity more accurately.
X-ray fluorescence (XRF) testing: This is a non-destructive technique that uses X-rays to analyse the composition of gold. It identifies the proportion of gold and other metals, including copper, silver and zinc, without melting the jewellery. However, surface-based readings may not always reveal variations in the internal composition.
Acid and touchstone test: In this traditional method, a jeweller rubs the gold against a testing stone and applies suitable testing acid to the resulting streak. The reaction helps estimate the metal’s karatage.
Fire assay test: Considered a highly accurate method for determining gold content, fire assay involves processing a small sample to separate gold from other metals. The remaining gold is weighed to establish its purity. However, the procedure is destructive because it requires a sample of the jewellery.
Gold purity according to karatage
Gold purity is measured in karats, with 24-karat gold representing the highest standard of purity commonly used in the market.
24 Karat (999) – 99.9% – Coins and bars
22 Karat (916) – 91.6% – Traditional jewellery
18 Karat (750) – 75% – Diamond and gemstone jewellery
14 Karat (585) – 58.5% – Contemporary jewellery
What should consumers remember before buying gold?
Home-based tests can provide preliminary indications of possible adulteration, but they cannot establish the exact karatage or purity of gold jewellery.
Consumers should prioritise BIS-hallmarked jewellery carrying a verifiable HUID code, purchase ornaments from repu
ted jewellers and insist on a proper invoice.
If there are doubts about the quality of an existing ornament, professional testing at a recognised hallmarking centre is a more dependable option than relying on household tests.
