Gem-quality synthetic diamonds are becoming increasingly available in the jewelry marketplace, and they have a place in the jewelry market as long as they are correctly identified and appropriately priced. Studies published over the past 30 years have resulted in an understanding of their production methods and means of identification. They can sometimes be recognized by a trained gemologist, but in the absence of distinctive visual features, positive identification requires examination by an experienced gem-testing laboratory. The traditional method of creating diamonds involves high pressure and temperature (HPHT) flux growth from a molten metal alloy to produce cuboctahedral-shaped crystals that have a flat base. The other method, called chemical vapor deposition (CVD), involves growth at high temperatures and very low pressures in a vacuum chamber to produce tabular crystals. Both methods can be used to produce colorless and colored synthetic diamond crystals. Differentiation of natural from synthetic diamonds is based upon recognizing the evidences of ancient growth and prolonged residence at high temperatures and pressures deep in the earth versus very recent and rapid growth of diamond in the laboratory or factory. Some of the instruments being developed for use by a jeweler to check for synthetic diamonds will be discussed.