Checking purity and avoiding fakes

Fake and low-purity gold is common, especially in informal markets. A few habits protect you.

Hallmarks and stamps

Real gold is usually stamped with its purity, such as 999, 916 or 750, and often with a maker's or assay office mark. Bars from reputable refiners show the refiner's name, the weight, the purity and a serial number, and come with a certificate. A stamp alone proves nothing, because stamps can be faked, but a missing one is a reason to be careful.

Buy from reputable sellers

The large international bars traded in London are made by refiners on the LBMA Good Delivery list. Look for well known refiners and established dealers that give receipts, have a real address and offer to buy back what they sell.

Tests and their limits

• Magnet test. Gold is not magnetic. If an item sticks strongly to a magnet, it is not solid gold. Passing proves little, because many fakes use metals that are not magnetic either.
• Weight and size. Gold is very dense, so a fake of the right size is usually too light. That is why sophisticated fakes use tungsten, which is almost as dense as gold.
• Acid test. Jewellers test the surface with acids. It can miss a thick layer of plating.
• XRF scan. An electronic scan that measures the metals in an item without damaging it. Many dealers and jewellers offer it, and it is the most practical check for most people.
• Assay. A laboratory melts and analyses a sample. Definitive, but it destroys part of the item.

Red flags

• A price well below the spot price. Real gold is almost never sold cheap.
• Pressure to decide quickly, or cash-only deals with no receipt.
• A bar with no certificate or serial number.
• A seller who will not let you have the item tested.