Beryl-II, a high-pressure phase of beryl: Raman and luminescence spectroscopy to 16.4 GPa

High-pressure study of dravite tourmaline: Insights into the accommodating nature of the tourmaline structure

“…Under compression the intensity of the R-lines decreases: this is likely primarily associated with the transition metal absorption bands migrating away from our excitation wavelength of 532 nm. Moreover, the disappearance of the broad 4 T 2 -associated band shows that a transition from an intermediate to strong crystal field occurs in the first few GPa of compression, which is consistent with previous observation in other Cr-bearing oxides (Dolan et al 1986;de Viry et al 1987;Hommerich and Bray 1995;Grinberg and Suchocki 2007;O'Bannon and Williams 2016b). As at 300 K, it is difficult to fit four bands under the 2 E region under compression, so we fit the spectra with three bands: based on our 77 K assignments, these are associated with the R 1 and R 2 peaks of Cr 3+ and the R 1 peak of V 2+ .…”

“…These powder diffraction studies provide insights into how the unit cell responds to compression, but they do not elucidate the positional changes of the individual atoms in the unit cell (Li et al 2004;Xu et al 2016). This is in contrast to other ring-silicates such as cordierite [(Mg, Fe) 2 Al 3 (AlSi 5 O 18 )] and beryl [Be 3 Al 2 (Si 6 O 18 )] which each show extensive high-pressure polymorphism (Prencipe et al 2011;Miletich et al 2014;Scheidl et al 2014;Finkelstein et al 2015;O'Bannon and Williams 2016b). Both cordierite and beryl undergo high-pressure phase transitions that involve distortion of the Si 6 O 18 ring.…”

Hydroxylherderite (Ca2Be2P2O8(OH)2) stability under extreme conditions (up to 750°C/100 GPa)

“…Besides, this information could help to explain beryllium deposit formation. 18 As far as we know, less than 10 Be-containing minerals were studied under high-pressure conditions, among them are beryl Be 3 Al 2 Si 6 O 18 , 19,20 chrysoberyl BeAl 2 O 4 , 21,22 phenakite Be 2 SiO 4 and bertrandite Be 4 Si 2 O 7 (OH) 2 , 23 behoite Be(OH) 2 , 24 londonite CsBe 4 Al 4 (B 11 Be)O 28 , 25 hurlbutite CaBe 2 P 2 O 8 , 26 and hingganite-(Y) Y 2 □Be 2 Si 2 O 8 (OH) 2 . 27 Of these, only hurlbutite was studied up to the amorphization (above 90 GPa), whereas all other minerals were studied up to 5-50 GPa, and these pressures are not their whole stability range.…”

First-Principles Study of Optical Absorption Energies, Ligand Field and Spin-Hamiltonian Parameters of Cr3+ Ions in Emeralds

“…To rationalize the different properties between natural and synthetic gemstones, spectroscopy is a very helpful tool for structural refinement, detection of impurities, and identification of structural water, among many other uses. In fact, numerous experimental techniques such as Fourier transform infrared spectroscopy, Raman spectroscopy, UV–vis–NIR spectroscopy, PL, spectral hole-burning, and electron paramagnetic resonance (EPR) spectroscopy have been employed to study both natural − and synthetic emeralds. ,− Furthermore, various spectroscopic studies comparing natural and synthetic emeralds found remarkable differences between them. − …”