... are similar, but c is approximately a third of that for a previously reported topaz-OH (denoted topaz-OH I). The structural formula of topaz-OH II can be written as (Al 0.68 Si 0.32 )(O 0.66 (OH) 0.34 ) 2 , suggesting significant cation disorder in the structure. The crystal structure of topaz-OH II is solved...

... derivatives of the bands initially at 3599 and 3522 cm −1 were −5.2(2) and −2.56(6) cm −1 /GPa, respectively. This contrasting behavior between the two forms of topaz at high pressures suggests that the OH substitution for F in topaz affects the hydrogen-bonding behavior under high pressure. * E...

...Augusta ALBERICO; Simona FERRANDO; Gabriella IVALDI; Giovanni FERRARIS Abstract An OH-rich topaz, Al 2 SiO 4 F 1.4 OH 0.6 , occurring in a kyanite quartzite of the Sulu UHP terrane (eastern China) has been optically and chemically (electron microprobe) characterised and its crystal structure...

... dependence of these factors can also affect the strength of hydrogen bonding. The relative significance of these factors may be investigated from high-pressure crystallographic studies of the mineral topaz. Topaz [Al 2 SiO 4 (OH,F) 2 ] is a well-known accessory hydrous mineral with a limited range...

... Mineralogical Society of America 2017 Topaz DFT B3LYP equation of state elastic constants athermal limit Topaz is an orthosilicate mineral with ideal formula Al 2 SiO 4 (F,OH) 2 , which is usually found as an accessory mineral in fluoride-rich granitic rocks related to pneumatolithic...

... analysis, the X-ray and neutron diffraction experiments, and the IR measurements. Topaz [ideal formula Al 2 SiO 4 (F,OH) 2 ] is one of the most important F/OH-bearing silicates, and is found as accessory mineral in F-rich granitic rocks (or in detrital sediments near areas of acid intrusive rocks...

...Kako Aradachi; Morihisa Hamada; Kiyoshi Tsuge; Tohru Watanabe Abstract Topaz, Al 2 SiO 4 (OH) x F (2– x ) , may play a significant role in transporting water and fluorine into the Earth’s interior at subduction zones. Seismological detection of topaz gives us insights into the transport mechanisms...

...Earl F. O'Bannon, III; Quentin Williams Abstract Topaz [Al 2 SiO 4 (F,OH) 2 ] is a subduction-related mineral that is found in metasediments and has a large pressure and temperature stability field. Here, we use luminescence spectroscopy of Cr 3+ to probe the Al site in topaz at pressures up to ~60...

... with a range of 29 Si chemical shifts (−130 to −190 ppm), a small fraction (2–3%) of tetrahedral Al, and a range of (and overall shorter) hydrogen-bonding distances than topaz-OH I. Therefore, the phase transition from topaz-OH I to II is characterized by both a significant increase in the occupied octahedral...

...Xianyu Xue; Masami Kanzaki; Hiroshi Fukui; Eiji Ito; Takafumi Hashimoto Abstract Topaz-OH, phase egg, and δ-AlOOH are hydrous phases in the Al 2 O 3 -SiO 2 -H 2 O system that have been found to be stable at successively higher pressures up to those corresponding to the lower mantle, and thus...

..., Mg, Ca, Al, Fe, and Si being analyzed. The resultant formulae of our samples of these minerals are Al 2 SiO 4 (OH, F) 2 for topaz, and CaAl 2 Al 0.53 Fe 0.46 Si 3 O 12 (OH) for clinozoisite. We did not probe for fluorine, but by measuring the b parameter coupled with the systematics of Ribbe...

...Marc Blanchard; Etienne Balan; Kate Wright Abstract The structures, infrared active OH stretching modes, and relative energies of OH-defects in ringwoodite (γ-Mg 2 SiO 4 ) have been studied by first-principles calculations based on density functional theory (DFT). Two types of fully protonated...

...Mainak Mookherjee; Wendy R. Panero; Bernd Wunder; Sandro Jahn Abstract Phase egg, [AlSiO 3 (OH)], is an aluminosilicate hydrous mineral that is thermodynamically stable in lithological compositions represented by Al 2 O 3 -SiO 2 -H 2 O (ASH) ternary, i.e., a simplified ternary for the mineralogy...

...Nao Cai; Toru Inoue; Kiyoshi Fujino; Hiroaki Ohfuji; Hisayoshi Yurimoto Abstract A new Al-bearing hydrous Mg-silicate that we named as 23 Å phase was synthesized at 10 GPa and 1000 °C, while also coexisting with diaspore and pyrope in the following system: phase A [Mg 7 Si 2 O 8 (OH) 6 ] + Al 2 O 3...

... Society of America 2023 Mineralogical Society of America Crystal structure EXAFS igneous rocks magmatic gas rhyolite silicates single-crystal EXAFS topaz trace elements vapor phase X-ray absorption spectroscopy Experimental Halogens in Honor of Jim Webster Topaz, Al 2 SiO 4 (F,OH...

...)], indicating 35–55% substitution of F by OH. Such naturally occurring, hydroxyl-rich topaz has not been previously reported. Some topaz grains from the HP belt show distinct zoning: (1) decreasing F content from narrow cores (13.3–16.5 wt%) to thick rims (9.5 wt%) or (2) oscillatory zoning (9.44–12.77 wt...

... ; Breiter et al. , 2013 ; Agangi et al. , 2014 , 2016 ). * E-mail: [email protected] Topaz is a F/OH-bearing nesosilicate, Al 2 SiO 4 (F,OH) 2 , that is usually found as an accessory and late-stage crystallization mineral in a wide variety of geological settings, such as F...

... and triploidite, which are monoclinic Mg, Fe and Mn phosphates with the formula Me 2+ 2 PO 4 (F,OH), constitute a modulated series based on the average triplite structure. Modulation occurs along b and may be commensurate with (2 b periodicity) or incommensurate but generally close to integer values (~3 b , ~5 b...

... AlSi 3 OH = δ-AlOOH + SiO 2 (stishovite) and the evolution in the elastic moduli and sound velocities of hydrous minerals as a function of density. * E-mail: [email protected] Copyright © 2022 by the Mineralogical Society of America 2022 Mineralogical Society of America * E-mail: msong...

... (= phase G); Cpv: Ca-perovskite. Hydrous phases present in pelagic sediments can be estimated based on phase relations in the Al 2 O 3 -SiO 2 -H 2 O system. Diaspore (AlOOH) and phase Π [Al 3 Si 2 O 7 (OH) 3 ] are stable to pressures of 6 GPa, and these phases react with SiO 2 to form hydrous topaz...