gemologists have dedicated much time and attention to separating natural from synthetic
diamonds, and natural-color fromtreated-color diamonds. Initially, these determinations
were based on systematic observations madeusing standard gemological tools such as a microscope,
desk-model (or handheld) spectroscope, andultraviolet (UV) lamps. While these tools remain
valuable to the trained gemologist, recent advances in synthetic diamond growth, as well as irradiation and high-pressure, high-temperature (HPHT) treatment techniques, have rendered them less definitive in identifying synthetic and color-treated diamonds.Thus, most gemological laboratories now use more-sophisticated scientific techniques such asabsorption and photoluminescence spectroscopy to detect treatments and synthetics.These developments in gem diamond identification have introduced many scientific terms and concepts into the gemological literature. One of the most important of these concepts is diamond “type.” The diamond type classification system is widely used in diamond research, because it provides a convenient way to categorize diamonds based on their chemical and physical properties. Understanding this system is