Quick summary: Industry experts have issued a warning that counterfeit and laboratory-grown diamonds are becoming increasingly difficult to detect, with many sophisticated simulants successfully fooling buyers on online marketplaces and within family collections. While laboratory stones share identical chemical properties but cost up to 85% less than natural diamonds, consumer reliance on unverified internet hacks or solo inspections regularly results in severe financial deception. For public policy and consumer financial well-being, enforcing stricter hallmarking regulations and promoting independent laboratory verification is vital towards preventing widespread fraud, stabilizing marketplace trust, and protecting vulnerable buyers from predatory sales tactics.
Shoppers are being warned that fake diamonds are becoming harder to spot, from inherited engagement rings tucked away in boxes to “bargain” jewellery listed on online marketplaces.
While some counterfeits are obvious, experts say many are now convincing enough to fool buyers who do not know what to look for. Jewellery expert Mark Conway, of MJJ, has revealed the warning signs people should check before buying diamonds, or when looking through family heirlooms at home.
“Most people think they’d spot a fake straight away, but the reality is that some counterfeit jewellery is much better than people expect,” said Conway.
“The biggest red flag is usually the deal itself. If someone is selling a diamond ring for a fraction of what it should be worth, there is usually a reason. That doesn’t always mean it’s fake, but it does mean you should slow down, ask questions, and get it checked before handing over any money.”
Conway also warned that online marketplaces can be particularly risky, especially when sellers use pressure tactics or refuse proper checks.
“A genuine seller should understand why you want to have something checked. If they try to rush you, become defensive, or won’t let you get an expert opinion, that should immediately set alarm bells ringing.”
Sparkle is not proof of authenticity
“One of the biggest mistakes people make is assuming that sparkle equals value,” Conway said. “Cubic zirconia and moissanite can both look very bright, and to an untrained eye they can easily be mistaken for diamonds. If the stone gives off an exaggerated rainbow sparkle, almost like a disco ball, that can be a clue that it might not be a natural diamond. That does not prove it is fake, but it is a reason to have it checked properly.”
The setting can reveal as much as the stone
Conway warned that the ring itself can be just as telling as the diamond it holds. “If someone is claiming a piece has a valuable diamond, look at what it is set in. A high-value diamond is usually set in good-quality precious metal. If the claws look uneven, the stone looks loose, or the metal feels poor quality, that should make you pause.”
He advised checking inside the band for a hallmark, which confirms whether the item is made from a precious metal such as gold or platinum. A hallmark consists of three parts: the assay office mark, the sponsor mark, and the metal fineness mark. According to Conway, a stamp showing only a number such as 375, 750 or 950 to indicate the metal is a sign the item could be fake.
“The setting will not give you the full answer, but it can tell you whether the piece feels consistent with what the seller is claiming.”
UK hallmarking rules require compulsory marks, including the sponsor’s mark, fineness mark, and assay office mark, on precious metal items to confirm authenticity and purity.
Online tests are not reliable proof
Conway said shoppers should not rely on social media hacks or DIY tests when checking diamonds at home. “There are lots of tricks online, from breathing on the stone to seeing if it sinks in water, but none of these should be treated as proof. They might give you a clue, but they will not confirm exactly what the stone is.”
He added that laboratory-grown diamonds can only be detected using specialist laboratory equipment, meaning a stone can look like a diamond and still be man-made. Lab-grown diamonds share the same chemical and optical properties as natural ones, but cost up to 85% less.
“If it is an heirloom, an engagement ring, or something you are thinking of buying, it is always safer to have it checked by a professional.”
Paperwork needs to match the stone
Conway said certificates and receipts can be useful, but buyers should not trust them blindly. “Paperwork is important, but it has to match the item in front of you. If a diamond comes with a certificate, check that the details line up with the stone being sold. That includes the carat weight, cut, colour, clarity, and any identifying numbers.”
“Fake paperwork does exist, and genuine paperwork can also be paired with the wrong item. If you are buying an expensive diamond privately, do not be afraid to ask for the stone to be checked before you pay.”
Concerns around diamond authenticity have grown alongside the expansion of online sales platforms, where simulants and laboratory-grown stones have at times been misrepresented as natural diamonds. Experts consistently recommend independent verification through reputable jewellers or certified laboratories for any high-value transaction or family piece of uncertain origin, to help protect buyers from financial loss and support informed decisions.