Fluorescence as a Tool for Identifying Treatment. Although we tested a limited number of samples, some differences in the fluorescence behavior of natural and treated diamonds were observed. In diamonds with H3 or 480 nm band defects, 3D fluorescence spectra did not show significant differences between the natural-color and treated samples. Yet treated diamonds tended to show much more fluorescence from the (N-V)– center, partially overlapping with the band from the (N-V)0 center, whereas naturally colored stones showed a dominant (N-V)0 defect (again, see figure 10). Because the fluorescence from the (N-V)– center was much more intense in the treated diamonds and shifted to longer wavelengths of 750 nm, the fluorescence color from the treated diamonds with both N-V centers was a more intense red color than in the untreated samples with only the (N-V)0 center, which produced an orange color. While this trend for N-V centers after HPHT treatment is well documented (e.g., Fisher and Spits, 2000) and also proved true in this study, gemologists should not rely solely on the observation of orange or red fluorescence to ascertain diamond treatment.