Multiple luminescent spectroscopic methods applied to the two related minerals, leucophanite and meliphanite

The photo-, cathodo-, radio- and ionoluminescence of two related beryllium minerals, leucophanite and meliphanite, have been determined. Meliphanite is an efficient luminescent mineral and has similar luminescence to leucophanite. Both leucophanite and meliphanite efficiently transfer energy to all activators in the sample either from the conduction or through a charge transfer band. We infer that coupling of the luminescence centre and lattice is important for interpreting rare earth element (REE) luminescence. Furthermore, changes in the relative intensity between REE emissions during sample degradation by CL demonstrate that each REE interacts differently with the host. Conversely, when a specific energy level of one REE is targeted in photoluminescence, no energy transfer to other REEs is observed despite many REEs having similarly spaced energy levels. This demonstrates that absorption and luminescence within an individual REE can be considered as intra-ion energy cascades, with little or no energy transfer to other REEs. Anomalous behaviour in the temperature dependence of IL in one leucophanite sample is interpreted as phase transitions in ice hosted in fluid inclusions. A comparison of luminescence of powder and cleavage fragment reveals that some emissions in the UV-blue region are surface related and do not represent bulk luminescence.