Absorption and PL Spectroscopy. The UV-Vis-NIR spectra of samples 21 and 22 featured a broad 550 nm band (thought to be caused by plastic deformation) that contributed to their pink color, as well as the (N-V)– center at 637 nm. FTIR indicated type IIa stones with no measureable nitrogen or hydrogen impurities. PL spectra showed evidence for significant concentrations of (N-V)0, H3, and (N-V)– defects (figure 10D). For samples 23 and 24, UV-Vis spectra indicated an abundance of (N-V)– centers; FTIR identified them as type IaAB with traces of isolated nitrogen. PL spectra showed both (N-V)0 and (N-V)– centers as well as H3 defects. For sample 25, UV-Vis spectra indicated the presence of a strong (N-V)– center and FTIR demonstrated a low concentration of type Ib isolated nitrogen defects. PL spectra showed both (N-V)0 and (N-V)– centers, together with H3 centers.