Chemical Formula: Ca4(Na,Ca)4Be4AlSi7O24(F,O)4
Status: IMA-GP
Mineral for Display: No
UV Type | Main color | Intensity | Observation Frequency |
---|---|---|---|
Long Waves (365nm): | Violet Pink | Short Waves (254 nm): | Violet Pink |
Other colors MW: | Violet Pink , Purple pink , | ||
Other colors SW: | Violet Pink , Purple pink , |
Most Common Activator: Eu2+
Other activators: Ce3+ ,
Peaks in the spectrum (nm):
Ce3+? repl. Ca2+ Eu2+? repl. Ca2+ : 450nm
The application of multiple forms of excitation (Friis et al. 2011) revealed that the UV-Blue emission in leucophanite and meliphanite consists of more than one emission center and is therefore more complex than previously thought. The most likely centers are defects related to the structure, e.g. in connection with the tetrahedral sites, and a Ce3+ center. The difference in Na/Ca ratio between the two minerals make it possible for REE to substitute into two sites in meliphanite contrary, to just one in leucophanite. The lower total REE content in meliphanite compared to leucophanite is consistent with a model whereby the formation of clusters is reduced and consequently generates sharper line emissions. The small difference in the average bond-length of the Ca coordination between the two minerals is consistent with the shift observed in the position of the Mn2+ emission. The excitation of specific REE in both leucophanite and meliphanite show that very little energy transfer occurs between different REE.
Conversely, excitation through the lattice excites all emission centers.
Both leucophanite and meliphanite have excellent luminescence properties, especially at low dopant levels.
Furthermore, the structural difference between the two related species indicates that meliphanite might be a promising phosphor. (Gaft)
(*)Data are not exhaustive and are limited to the most important localities for fluorescence
http://www.mindat.org/show.php?name=Meliphanite
http://webmineral.com/data/Meliphanite.shtml
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