What are they? Lab-grown diamonds have always been viewed as a possibly formidable competitor to natural (mined) diamonds. Unlike simulants, the stones are diamonds—chemically, physically, and visually—but they have been produced in a lab rather than from a mine. For a long time, companies could manufacture only yellows and other fancy colors, rather than colorless gems, because “white” gems often cost too much to produce. Now, they hope to increase their production of colorless gems.

Are they detectable? While most jewelers and dealers cannot tell these diamonds apart visually, they are detectable by gem labs and with the proper equipment. GIA’s Shane McClure says he’s confident the Institute can spot every single one. In addition, Gemesis and other manufacturers sell them with lab reports and inscriptions. “Occasionally people ask us to take the inscriptions off, and I tell them we won’t do that,” says Gemesis CEO Stephen Lux. “No one in the trade wants things to be clear to consumers more than us.”

What are the laws ­regarding them? According to the FTC’s Guides, when sold, these diamonds must be ­preceded by the words laboratory-grown, laboratory-created, [manufacturer name]-created, or synthetic. The word cultured, several companies’ term-of-choice, can be used, but only in conjunction with the other terms, the FTC has ruled. Simulants like cubic zirconia cannot be called ­synthetics or similar names under the Guides.