Published 2 June 2026
Start with the hallmark
British gold has been hallmarked for over six hundred years. A UK assay hallmark consists of four marks: the maker mark, the standard mark (showing fineness), the assay office mark and the date letter. The most common fineness marks on gold are 375 (9 carat), 585 (14 carat), 750 (18 carat), 916 (22 carat) and 999 (24 carat). The standard mark is sometimes a crown over the carat number on older pieces.
A hallmark is not absolute proof. Some unhallmarked gold is genuine, particularly Indian, Middle Eastern and antique pieces. Some hallmarks are forged. But on a modern British piece a clear hallmark is the strongest single home indicator of authenticity.
Weight, density and feel
Gold is heavy. Real gold feels dense for its size in the hand. Gold-plated brass or pewter pieces feel light when you weigh them on a kitchen scale next to a known-gold piece of the same dimensions. Pure gold has a density of 19.32 grams per cubic centimetre. Tungsten, the metal counterfeiters use to fake heavy gold, has a density of 19.25, almost identical, which is why XRF beats the kitchen scale on suspect bars.
Water displacement is the home version of a density test. Lower the item on a thread into a measuring jug, note the water-level change in millilitres, and weigh the dry item on a scale. Divide weight by displacement and you get density. A gold ring should read very close to 19 g/cm3. A clearly underweight reading is a red flag.
The magnet test
Gold is not magnetic. A strong neodymium magnet should not stick to a real gold ring. If a magnet pulls on the item, the item contains iron or a magnetic alloy and is not solid gold. The reverse is not always true: many fakes use non-magnetic base metals like brass, so a non-magnetic reading by itself does not prove gold. The magnet rules things out, not in.
The ceramic and vinegar tests, handle with care
The traditional ceramic streak test rubs the item on an unglazed ceramic plate. A gold streak says gold. A black streak says the item is not gold. The problem is that the test scratches the piece. We strongly recommend against the streak test on hallmarked jewellery, antique items or anything with sentimental value. The damage is permanent and can knock more off the offer than the test was worth.
The vinegar test pours household vinegar on the item. Real gold does not react. Plated or base-metal items may dull or discolour. The vinegar test sometimes damages surface finish on plated pieces and is messy. Again, we recommend against it on anything you might want to sell at full value.
The skin discolouration myth
A common belief holds that real gold leaves a green or black mark on your skin. This is not actually how it works. Pure 24 carat gold does not react with skin. Lower-carat gold (9 carat and 14 carat especially) contains copper, which can react with sweat to leave a faint mark on some people. The skin mark therefore tells you the item contains some copper alloy. It does not tell you whether the piece is gold or base metal.
Treat skin discolouration as neutral information, not as a verdict either way.
Wear points and where to look for plate
Examine the high-wear areas on the piece, the inside of a ring shank where it has rubbed against a finger, the outside curve of a bangle, the back of a watch where it has worn against the skin. On a plated piece the gold layer wears through first at these points, exposing the base metal underneath as a darker, duller patch. On a solid gold piece, the wear surface looks the same all the way through.
A loupe (10x magnification) helps. Hand-held jewellers loupes are inexpensive and let you see the wear pattern clearly.
When to stop testing and post for XRF
XRF testing is non-destructive, quick and definitive. The analyser reads the alloy in seconds and tells us exactly what carat the metal is. Once you have looked at the hallmark, felt the weight, run a magnet over it and inspected the wear points, you have done as much as you usefully can at home. Anything further risks damage.
GoldPaid tests every item received, free, with a full written valuation. WhatsApp photos to 07763 741067 and we will tell you whether your item is worth posting. Your parcel is insured up to £2,500 via Royal Mail Special Delivery. Final offers depend on inspection, item weight, purity, hallmarks, stones, non-gold components, condition and the live precious-metal market.
Common questions
Is the magnet test definitive?
No. It rules out iron-containing fakes. It does not rule in non-magnetic base metals.
Should I acid-test my jewellery?
We recommend against it. Acid damages the surface and reduces resale value. XRF gives the same answer without damage.
Why does my gold leave a green mark?
Lower-carat gold contains copper. Copper reacts with sweat. The reaction is not a sign of fake gold.
How accurate is the water-displacement test?
Useful for orientation. Not accurate enough to distinguish 18 carat from 22 carat. XRF is the definitive method.
Are old unhallmarked rings always fake?
No. Antique, Indian, Middle Eastern and some continental gold is unhallmarked but genuine. Post it in for XRF.
Can I tell carat from colour?
Only roughly. Higher carat tends to look more yellow. Lower carat tends to look paler or whiter. XRF is the only definitive test.
What does GoldPaid charge for testing?
Nothing. Testing, written valuation and return post if you decline are all free.
How do I send my item?
WhatsApp photos to 07763 741067 first. You get a shape-of-offer reply and a prepaid Royal Mail Special Delivery label.