The short answer
No single home test proves a coin is real gold. The most reliable approach is to combine several non-destructive checks (weight, dimensions, density, a magnet and a close visual inspection) and then, if the coin is valuable or you are still unsure, have it checked by a reputable dealer using an electronic tester or XRF analyser.
Start with weight, size and appearance
Genuine coins are made to tight specifications. Look up the published weight, diameter and thickness for your coin and year, then measure with a digital scale (ideally to 0.01 g) and calipers.
- A fake that matches the weight is often thicker or wider, because gold is very dense.
- A fake that matches the size is often too light.
- Under magnification, check that the design is crisp, the lettering is even and the edge matches the genuine coin (reeded, lettered or plain). Cast fakes may show tiny bubbles, soft details or a rough surface.
Remember that purity differs by coin. A British Sovereign is 22 karat, so judge it against its own specifications, not those of a pure 24 karat coin. See our guides on what gold coins are made of and identifying gold sovereign coins.
The magnet test
Gold is not magnetic, so a coin that clearly sticks to a strong magnet is not gold. This is a quick way to rule out iron, steel or nickel fakes. It cannot confirm a coin is gold, because many fake materials such as brass, copper, lead and tungsten are also not magnetic. Our article on whether gold coins are magnetic explains the test in more detail.
Density test
Pure gold has a density of about 19.32 g/cm³. Measuring density can expose fakes that match the weight and size of a genuine coin.
- Weigh the coin in air.
- Weigh it again while it is suspended in water on a thread.
- Divide the weight in air by the difference between the two weights, which gives the density in g/cm³ (since water is about 1 g/cm³).
Gold alloys will read lower than pure gold, so compare the result with the expected figure for that coin’s alloy. Small weighing errors lead to large density errors on a small coin, so treat the result as a guide.
Ping test
Balance the coin on a fingertip and tap it with another coin or a small piece of metal. Many gold coins give a clear, sustained ring, while base metals tend to sound duller. The test is subjective, and apps that analyse the sound exist, but results depend on the coin, the surface and the alloy. Use it as a supporting clue rather than proof.
Tests to avoid on coins
- Acid tests use nitric acid or a testing kit on a scratched or marked spot. They can damage a collectable coin and reduce its value, and acids are hazardous to handle.
- Ceramic scratch tests involve dragging the coin on unglazed ceramic, which marks the coin.
- Vinegar is sometimes suggested online, but it is not a reliable way to test gold, and it can affect the surface of a coin.
If a coin has numismatic value, avoid anything that scratches, etches or stains it.
Electronic testers and XRF
Dealers often use electronic precious metal verifiers, which pass electromagnetic waves through the coin and measure its conductivity, or XRF (X-ray fluorescence) analysers, which report the metals at the surface. These are non-destructive. Note that XRF mainly reads the surface layer, so a thick plating over a base core can still mislead, which is why dealers combine it with weight and dimension checks.
Tungsten and gold-plated fakes
Tungsten has a density very close to gold, so a tungsten core with a gold layer can match both the weight and size of a genuine coin. Plated fakes may also pass a magnet test. This is why weight, size, conductivity and professional testing all matter. For high-value purchases, buy from reputable sources that guarantee authenticity.
How much does testing cost?
Prices vary by country, dealer and method. Some coin shops will do a quick check for free or for a small fee, and formal authentication or grading services charge according to the coin’s value and the service level. Ask for a quote before handing over your coin.
Can you track a gold coin?
Individual coins generally do not have serial numbers or tracking, unlike some bars. Some modern mints add security features such as micro-text or special surface patterns. Keep your purchase invoice, which is the record of where a coin came from.
FAQ
Is gold from big dealers real? Large, established dealers have reputations to protect and typically guarantee authenticity, but you should still keep your receipts and check any coin on delivery.
What color does fake gold turn? Plating can wear to show a different base metal underneath, often a reddish, silvery or greyish tone. Do not rely on chemical tests to see this.
What should I do if I think my coin is fake? Stop testing, photograph the coin, and take it to a reputable dealer or authentication service. If you bought it recently, contact the seller.