Luminescent centres in pezzottaite, CsBe2LiAl2Si6O18

Pezzottaite, CsBe2LiAl2Si6O18, is a rare new pink mineral found in central Madagascar and Afghanistan, exhibiting a beryl-like trigonal reduced symmetry (R3c). Numerous data on its optical properties, Raman, IR, absorption spectra as well LIBS data are available, while it is described as a non-luminescent mineral under UV light. However, pezzottaite shows several laser-induced red emissions and a particular unusual blue luminescence. LIBS analysis reveals the presence of Sc, Ca, Sr, Na, K and Rb as substituted trace elements, but these elements cannot be considered as the centres responsible for the observed emissions. Time-resolved analyses under different excitations (266, 355, 514 and 532 nm) at room and liquid nitrogen temperatures allow the identification of Fe3+ (730 nm) and Cr3+ (699 nm) as red emitting centres, while Tl+ is considered responsible for the blue fluorescence (420-425 nm). Photoluminescence proves effective for identifying the presence of these luminescent trace elements even below the LIBS detection limit (a few ppm), but without yet attaining a quantitative resolution.