the colors tested. We believe this absorption is related to the starting material used for Be diffusion,rather than to the treatment itself. It must beemphasized, however, that this observation is in noway diagnostic of Be diffusion, as many natural yellow or orange sapphires show similar absorption.Color Distribution. Beryllium diffusion came to theattention of gemologists and the trade after yellowto-orange three-dimensional surface-conformal layers were seen on faceted orangy pink padparadschalike sapphires (McClure et al., 2002; Scarratt2002a,b). We have never observed—either in thecourse of this study or in our many years of experience—such a three-dimensional layer of color paralleling the surface of a natural-color polished gemstone. To the best of our knowledge, it can only becaused by a diffusion treatment.Therefore, careful observation of color distribution became critical to this investigation. Exami