Since Robert Crowningshield's discovery in the late 1950s that diamonds that have been artificially colored by irradiation and subsequent annealing could be identified by their characteristic ...

Figure 1. This 4.89 ct colorless synthetic sapphire was presented as a sapphire. Photo by Meenakshi Chauhan. A 4.89 ct colorless oval mixed-cut specimen was submitted as a sapphire to the Gem Testing ...