Over the past two years, the heat treatment of corundum involving lattice diffusion of beryllium (Be)at temperatures over 1800°C has become a major issue in the gem trade. Although initially onlyorange to orangy pink (“padparadscha”-like) sapphires were seen, it is now known that a full range ofcorundum colors, including yellow and blue as well as ruby, have been produced or altered by thistreatment. An extension of the current understanding of the causes of color in corundum is presentedto help explain the color modifications induced by Be diffusion. Empirical support is provided by Bediffusion experiments conducted on corundum from various geographic sources. Examination ofhundreds of rough and faceted Be-diffused sapphires revealed that standard gemological testing willidentify many of these treated corundums, although in some instances costly chemical analysis bymass spectrometry is required. Potential new methods are being investigated to provide additionalidentification aids, as major laboratories develop special nomenclature for describing this treatment.