The 10 Best Diamond Testers
This wiki has been updated 13 times since it was first published in April of 2018. Diamonds have been prized for thousands of years, and it's likely that fakes of these valuable forms of carbon have been around since their discovery. Luckily, prospective buyers can rely on more than just their eyes to weed out the frauds from the real deals. We've sorted through a wealth of cheap, knockoff electronic testers to bring you some of the most reliable detectors. When users buy our independently chosen editorial picks, we may earn commissions to help fund the Wiki.
November 16, 2020:
We had to remove the Gemetrix Melee Inspector in this update due to availability concerns. We added the Presidium Multi-Tester III, another high-quality product from the well-known brand, which boasts and intuitive display and pleasant appearance, though it misidentifies some diamonds as moissanite. We've added the DiamondNight Dual Tester as well, because it's a particularly inexpensive option that can distinguish between diamonds and moissanite, though it does not work for any other gems or metals.
There are many popular options out there that would, at first glance, appear as though they warrant a spot on this list. But almost all of them are, in fact, knockoffs of the HDE High Accuracy, so we've decided to keep them off the list and promote only the model that originally pioneered this design instead.
If you spring for an item like the Presidium Diamond Mate-C, which struggles to detect moissanite, you may want to purchase one of these UV flashlights for the added security of being able to run a UV light test on the stone.
August 29, 2019:
In ranking these diamond testers, we paid close attention to the method they used to identify fakes. Most devices on the market test for phosphorescence, hardness, and electrical and thermal conductivity. Knowing the strengths and limitations of each of these methods will help you make a better decision when it comes time to purchase a tester.
Synthetic moissanites, which are popular diamond alternatives, can often fool cheaper diamond testers, especially those that solely measure thermal conductivity, such as the Presidium Diamond Mate-C, since heat moves through both types of stone at about the same rate.
Moissanites also have a similar hardness to diamonds, so the HDE High Accuracy is better left for situations where you're trying to differentiate between natural gemstones instead of trying to detect lab-made ones.
Because they use a combination of testing methods, the Presidium Adamas and Gemlogis Mantis 3 in 1 are able to reliably test for synthetic gemstones, though they are pricier than many of their competitors.