In the past decade, laboratory-grown diamonds have grown in popularity, increased in size and improved in color and clarity, filling an important niche in the industry. We’ve seen laboratory-grown diamonds in larger sizes and higher quality than ever before pass through GIA.

In order to protect consumers and help them know exactly what they’re buying, we have developed advanced techniques to distinguish laboratory-grown diamonds from natural diamonds. Here is how the identification and analysis process works from beginning to end:

When a gemstone is first submitted, no assumptions are made and no possibilities are ruled out based on its visual appearance. What looks like a diamond may actually be a simulant, such as a cubic zirconia (CZ) or moissanite. Rather, the gemologist relies on scientific measures such as the stone’s refractive index, density, spectroscopy and more to determine its identity. If a stone is identified as a diamond, it is then tested to verify if it is natural, treated or laboratory-grown.

Laboratory-grown diamonds often have distinctive features such as graphitic or metallic inclusions (depending on the growth method), color zoning or graining patterns that can be seen under magnification. For example, the presence of nickel or other metals in a diamond, along with a lack of “natural” features, indicate that the stone is most likely an HPHT-grown diamond. That’s because HPHT diamonds often contain dark flux-metal inclusions from the chamber used in its growth process. CVD diamond, on the other hand, often contain dark graphitic inclusions. These characteristics can point scientists in a certain direction as to the diamond’s identity but aren’t always conclusive, however.

That’s why gemological laboratories also use absorption and luminescence spectroscopic techniques to identify diamonds. Some of these techniques involve using a spectrometer to measure a stone’s photoluminescence after it has been excited by laser or using deep UV to illuminate a stone for fluorescence imaging. Photoluminescence spectroscopy is able to show precisely and accurately the defects within each diamond that are distinctive of the diamond’s growth method. Under deep-UV illumination, an HPHT diamond will often display a cross-shaped pattern due to the way impurities concentrated when the stone formed. In some cases, HPHT diamonds can also exhibit phosphorescence, glowing after being exposed to UV light, even after the light source has been turned off.

In CVD diamonds, photoluminescence spectroscopy can reveal the presence of several “ingredients,” such as silicon, that are common to CVD diamonds. Under deep-UV illumination, CVD diamonds will also reveal that they grew layer by layer (like a stack of pancakes), a growth structure that is unique to diamonds with this growth method.

After scientists have identified a diamond as laboratory-grown, they then evaluate the stone as meticulously as they would natural diamonds. For added disclosure and identification, the laboratory-grown diamond’s girdle is laser inscribed with its report number and a statement that the stone is laboratory-grown. The LGDR that comes with a laboratory-grown diamond provides a full analysis of the specifications of the diamond, including the precise measurement and details involving the 4Cs – Color, Clarity, Cut and Carat weight. You can be sure that every gemstone that comes with a GIA report has received a reliable, objective evaluation of its identity and quality.