Start with the real defence
Before any test, the honest answer: the most effective protection against counterfeit bullion is not a gadget, it is provenance. Buying recognised products from a dealer who will buy them back, and keeping assay cards and tubes intact, prevents far more problems than any test detects after the fact.
That said, knowing how to check your own metal is worth an afternoon. Here is what actually works.
Weight and dimensions catch most fakes
This is the single most useful check, and it needs about $30 of equipment: a scale that reads to 0.01g and a set of digital calipers.
Bullion is made to tight tolerances, and counterfeiters have a problem — they cannot match weight and dimensions at once with a cheaper metal. A one troy ounce coin weighs 31.1034768 grams, and if the fake metal is less dense, matching that weight forces the coin to be physically bigger. Which is why so many fakes are subtly too thick.
A genuine one ounce American Silver Eagle, for example, is 40.6mm across, 2.98mm thick, and weighs 31.103g. Check all three. Two out of three is not a pass. Published specifications for any mainstream coin are available from the issuing mint, and it is worth looking them up rather than eyeballing it. If you are hazy on why bullion uses troy ounces at all, we cover it in why bullion is measured in troy ounces.
Density: why silver is hard to fake and gold is harder to check
Every metal has a characteristic density, and this is where the physics does the work for you:
- Gold: 19.32 g/cm³
- Silver: 10.49 g/cm³
- Lead: 11.34 g/cm³
- Copper: 8.96 g/cm³
- Tungsten: 19.25 g/cm³
Look at that last one. Tungsten sits within a whisker of gold, and it is cheap. That single coincidence is the reason essentially every serious gold counterfeit is tungsten based, and the reason a simple density test on gold is not conclusive on its own.
Silver has no such twin. Nothing cheap is close to 10.49, so density testing silver is genuinely informative. You can measure it at home by weighing the piece dry, then weighing it suspended in water, and dividing the dry weight by the weight difference.
The magnet slide test
Gold and silver are not magnetic, so a fake that sticks to a magnet is settled immediately. But the more interesting version uses a strong neodymium magnet on a tilted piece of silver: the magnet should slide down slowly, as if through treacle.
That drag is real physics — the moving magnet induces eddy currents in the highly conductive silver, which push back against it. Most counterfeit alloys are poorer conductors and the magnet simply slides off. It is a nice test because it is hard to fake and impossible to damage anything doing it.
The ping test
Balance a coin on a fingertip and tap it with another coin. Silver produces a distinctly high, clear ring that sustains for a couple of seconds. Base metal fakes produce a dull, short clunk.
Your ear is better at this than you would expect, especially with a known genuine coin to compare against. There are phone apps that analyse the frequency, and they are a reasonable second opinion. Treat it as a strong indicator rather than proof, and note it does not work on coins sealed in capsules or slabs.
The ice test
Silver is the most thermally conductive element there is. Put an ice cube on a silver bar at room temperature and it begins melting almost immediately, noticeably faster than on any base metal. It is a satisfying test, it costs nothing, and it is quite hard to argue with.
What not to do
- Do not acid test bullion. Acid testing is for scrap jewellery. It permanently marks the surface and will reduce what a dealer pays you.
- Do not bite it. This tells you nothing useful and dents soft metal.
- Do not clean or polish anything. Ever. It does not improve authenticity or value, and it reliably reduces both.
- Do not break a sealed assay card to test the bar. The intact packaging is a meaningful part of what makes it easy to sell.
- Do not rely on appearance alone. Modern counterfeits reproduce designs, mint marks and even serial numbers convincingly. The physical properties are what betray them.
When to get it checked properly
Home tests are good at catching crude fakes and reassuring you about ordinary purchases. They are not conclusive on a large gold bar, particularly against tungsten cores.
For that, dealers use equipment you would not buy for yourself: XRF analysers that read elemental composition without marking the surface, ultrasonic testers that detect a foreign core by measuring how sound travels through the piece, and conductivity meters that read through capsules and packaging.
If you have inherited metal, bought privately, or picked something up somewhere you are not certain about, having it professionally verified is worth doing before you build a plan around it.
Where risk actually concentrates
Counterfeits cluster in predictable places: private sales and online marketplaces, "too good to be true" pricing, unbranded bars with no assay documentation, and anything where the seller will not take it back. High value, widely recognised products are the most faked, precisely because they are the most liquid.
Buying from an established dealer, keeping documentation, and choosing recognised mint products handles most of this before it becomes your problem. Our guide to buying gold in New Zealand covers choosing a dealer in more detail.
Not sure about something you own?
Bring it in. We assess weight, purity, mint or refinery and condition as part of our buy back service, and there is no obligation to sell — if you simply want to know what you have, that is a fine reason to book. You can also get in touch first if you would like to describe it before making the trip.
Browsing rather than checking? Our silver range is a straightforward place to start.
This article is general information only. Home testing methods are indicators, not guarantees, and no single test is conclusive on its own. For anything of significant value, seek professional verification.
Visit the Williams Bullion showroom at 124 Peterborough Street, Christchurch Central 8011, or call +64 3 667 2327.