Synthetic - PL spectra Synthetic Index IR-Reflectance Photoluminescence UV-Vis-NIR CGS: Greenish-blue synthetic CGS:Cr4+ - 4.15 ct (synthetic melilite) Greenish-blue synthetic CGS:Cr4+ - 4.15 ct (synthetic melilite) No photoluminescence with the following sources: 254, 377, 405, 532 and 670 nm.