A common question when buying, selling or pledging gold is how to check gold purity. Even if it looks genuine, the appearance cannot tell you much about its purity. A gold item’s purity determines how much actual gold it contains. It also affects its value, resale price and gold loan eligibility.
So whether you are buying gold coins or jewellery, a gold purity test ensures you always get your money’s worth. Here is everything you need to know.
How Is Gold Purity Measured?
Gold purity indicates the percentage of actual gold present in an item. Since pure gold is too soft to make jewellery, it is often mixed with other metals like silver or copper to strengthen it. A gold purity test helps you determine the percentage of gold compared with the other metals mixed in.
Gold purity is generally expressed in karats (K)/(kt) or fineness. Karat divides a gold alloy into 24 equal parts to indicate how many parts are pure gold. 24K gold is considered the highest purity. Fineness expresses gold purity by splitting the alloy into 1000 parts. For example, 22K gold contains 22 parts gold out of 24, equivalent to approximately 91.6% purity or 916 fineness.
| Gold Karat | Gold Purity | Fineness | Common Usage |
|---|---|---|---|
| 24K | 99.9% | 999 | Coins and bars |
| 22K | 91.6% | 916 | Heavy jewellery |
| 18K | 75.0% | 750 | Fine or studded jewellery |
| 14K | 58.5% | 585 | Budget-friendly and everyday jewellery |
How to Check Gold Purity Using Hallmark
To identify gold purity, start by checking its hallmark. In India, the Bureau of Indian Standards (BIS) is the official authority for checking gold purity and assigning BIS hallmarks.
When you buy hallmarked gold jewellery, look for these three marks:
- BIS Logo: Confirms that the jewellery has been hallmarked under the BIS system.
- Purity Mark: Shows the gold’s purity. For example, 22K916 means the jewellery is 22-karat with 91.6% pure gold.
- HUID: A unique six-digit alphanumeric code given to individual gold jewellery pieces to prevent duplication or fraud.
You can also verify the HUID using the BIS CARE app. Enter the HUID under the ‘Verify HUID’ option to check the details of the hallmarked jewellery.
How to Check Gold Purity at Home: Basic Tests
Gold owners often want to know how to check pure gold at home. Here are some basic tests that may indicate impurities in your gold.
- Visual inspection: Look for the BIS hallmark, purity mark and HUID. Also check for signs of discolouration, peeling or uneven colouring, which may indicate gold plating.
- Magnet test: Gold is not magnetic. If the jewellery gets attracted to a magnet, it may contain a higher quantity of other metals or may be a sign of impure gold.
- Vinegar test: Place a few drops of white vinegar on the gold and leave it for a few minutes. Genuine gold generally does not react or change colour.
- Float test: Place the gold item in a container of water. Gold is dense and should sink to the bottom. If it keeps floating, it isn’t pure gold. However, other metals can also sink.
While at-home gold purity tests can indicate gold’s purity, they are not 100% conclusive. For more accurate results, always have a professional check your gold.
Professional Gold Purity Testing Methods
Professional gold purity tests are more reliable because they use specialised equipment and a controlled environment. The most commonly used methods are as follows:
- XRF Testing: X-ray fluorescence analyses the metals present in the gold and estimates its purity. This gold quality check is quick and does not damage the jewellery.
- Acid Testing: A small sample is tested with acids of different strengths. The reaction helps determine the approximate gold purity.
- Ultrasonic Testing: High-frequency sound waves examine the gold's internal structure. It can help identify inconsistencies or detect whether an item may have a different metal inside.
- Fire Assay: A small sample is melted and analysed to determine its exact gold content. It is highly accurate but destroys the sample, so it is generally used for specialised or laboratory testing.
How to Check If Gold Is Genuine?
- Check for the BIS hallmark and HUID. The BIS mark indicates that the jewellery has been hallmarked, while the HUID is a unique code that you can verify online.
- Look for the purity marking, such as 22K916, 18K750 or 14K585. This tells you the gold's karat and fineness.
- Examine the jewellery for peeling, discolouration or uneven colouring. If another metal is visible underneath, it could indicate gold plating.
- If the markings are missing or you are still unsure about the jewellery’s authenticity, get a professional gold purity test for a more reliable way to confirm its content.
If you are considering pledging your gold for a loan, knowing its purity can help you understand its potential value as collateral.
Manappuram Finance offers multiple gold loan options against eligible gold jewellery and coins. Use our gold loan calculator to check your potential loan amount and determine your eligibility using these gold loan eligibility criteria.
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