Stephan, T. ; Hutanu, V.MLZ* ; Li, X.MLZ* ; Lind, T. ; Müller, S.

2023

Abstract: The pink variety of beryl, morganite, is one of the most popularorangey-pink to pink gemstones. Its colour is attributedto manganese, both Mn2+ and Mn3+ (Nassau & Wood, 1968,Wood and Nassau, 1968, Schmetzer et al., 1974, Shigleyand Ford, 1984, Deer et al., 1992), which produce a seriesof spin-allowed absorption bands between 450 to 600 nm.Their exact position and quantity depends on the strengthand symmetry of the local crystal field, which, among others,also depends on the substitution mechanisms on theBe-position in the crystal lattice (Platonov et al., 1989). Bythermal enhancement, the colour of pink morganites isusually not influenced much (Schmetzer et al., 1975), however,orangey hues can be removed. By artificial irradiationthe colour saturation of colourless to pale pink manganese-bearing beryl is stronglyintensified, due to an intensificationof the manganese-band system (see also Schmetzeret al., 1975). Iron-bearing samples become orangey-pinkto brown, due to an additional intensification of the oxygen-metal-charge-transfer-band system (OMCT-band system,Fe3+-O2—CT). These samples can be heat treated afterirradiation, weakening the OMCT-band system again andresulting in pure pink colours.

Keyword(s): Instrument and Method Development (1st) ; Geosciences (2nd)

1. IRRAD (IRRAD)

1. Irradiation facility