A lab diamond is a real diamond in every way, but there are various methods used to identify it as laboratory-grown rather than mined. Consumers can perform some checks themselves, others require assistance of a jeweler and some tests are only available to the largest gem labs.
Most lab grown diamonds are fancy yellow or blue colors. These colors are very rare in nature and as a result are quite expensive and not commonly available. Diamonds with “fancy intense” or “fancy vivid” colors have a good chance of being lab grown, though the color alone is not a conclusive indicator.
All diamonds we sell over .30 carats are independently graded by a gemological laboratory, primarily IGI New York. The certificate clearly identifies the diamond as laboratory grown. The diamond itself is laser inscribed on the girdle with both the certificate number and language denoting the diamond as created, which can be read with 10x magnification.
Nearly all diamonds, mined and grown alike, have tiny inclusions that affect their clarity. Mined diamonds are grown in molten rock deep inside the earth and their inclusions are most commonly feathers, crystals, pinpoints and clouds. Lab grown diamonds are grown in a molten metal solution and as a result the most common inclusion is metallic. Metallic inclusions do not occur in mined diamonds, and these inclusions can usually be identified with 10x magnification. In diamonds with VS clarity or better, inclusions–regardless of type–cannot be seen with the unaided eye.
At the scientific level, diamonds can be categorized into four types, based on the impurities in the carbon lattice, at the atomic level. These impurities are not the same as inclusions, and need powerful equipment such as an infrared spectrometer to detect the type of a diamond.
- Type Ia – About 98% of mined diamonds
- Type Ib – All synthetic yellow diamonds, 0.1% of mined diamonds (fancy yellow & green)
- Type IIa – All synthetic colorless diamonds, 1-2% of mined diamonds (colorless & pink)
- Type IIb – All synthetic blue diamonds, 0.1% of mined diamonds (blue)
Diamonds can be tested with simple testers available at most jewelers. These commonly test for either thermal or electrical conductivity. Diamonds conduct heat very well, while most simulants do not. Thermal tests accurately identify lab diamonds as real diamonds.
Electrical conductivity tests are used to test for moissanite, since this simulant is electrically conductive. All yellow and mined white diamonds are not electrically conductive, however all blue diamonds–mined and grown alike–are electrically conductive, due to the boron in the diamond lattice. In addition, some HPHT-grown white diamonds have trace amounts of boron in them, so may be electrically conductive, despite being colorless. Electrical conductivity tests may be accurately used for yellow diamonds, mined and CVD-grown white diamonds though will give false positives for all blue diamonds, and may give false positives for some HPHT-grown white diamonds.
There are a few advanced machines that can correctly identify lab created diamonds. Fourier transform infrared spectrometer (FTIR) or energy dispersive X-ray fluorescence (EDXRF) can both detect traces of metal in a diamond, which comes from the molten metal solution the diamond is grown in.
A cathodoluminescence (CL) spectrometer can show different growth sectors in a diamond. Mined diamonds only have octahedral growth sectors, while in a vast majority of HPHT created diamonds, they have both octahedral and cubic growth sectors.
DeBeers has developed two machines that can properly identify synthetic diamonds. The first, DiamondSure, measures light absorption at a very specific wavelength and is used as a preliminary check. The more advanced and expensive DiamondView machine uses shortwave ultraviolet imaging to look at fluorescence patterns in the diamond. This machine is similar to the cathodoluminescence. Both of these machines are expensive and are usually only available at the major gemological labs like GIA, IGI and EGL.