... parameter refined from high-resolution synchrotron X-ray diffraction (XRD) data is a = 12.5056(5) Å, with Z = 8 (calculated density = 3.53 g/cm 3 ). Fourier-transform infrared spectroscopy spectrum of xuite shows absorption bands at 3682 and 3579 cm −1 , indicating the presence of OH – in the hydrogarnet...

.... Correlations among the constituents of ferrihydrite determined by electron microprobe, including anhydrous totals, indicate progress during the growth of two charge-balanced exchanges involving silica enrichment: an inverse cronstedtite substitution (MgFe 2+ ,Si) (Fe 3+ Mn 3+ ) –2 and an inverse hydrogarnet...

... of this study, the garnets appear to contain local microscopic- and nano-size Ca 3 Al 2 H 12 O 12 - and Ca 3 Fe 2 3 + H 12 O 12 -like domains and/or clusters dispersed throughout an anhydrous “matrix.” The substitution mechanism is the hydrogarnet one, where (H 4 O 4 ) 4– ↔ (SiO 4 ) 4– , and various local...

.... IR single-crystal spectra of several nominally anhydrous calcium silicate garnets, both “end-member” and solid-solution compositions, were recorded at room temperature and 80 K between 3000 and 4000 cm –1 . Five synthetic hydrogarnets in the system Ca 3 Al 2 (SiO 4 ) 3 -Ca 3 Al 2 (H 4 O 4 ) 3 -Ca 3...

... as shown by andradite. This behavior is indicative of the hydrogarnet substitution. The measured IR spectra of natural almandine- and pyrope-rich (Dora Maira, Italy) crystals, on the other hand, show different spectroscopic features with several OH – modes that are not consistent with the hydrogarnet...

... + = H + , Na, K, Li), can occur at the expense of the OH – group coordinating one of the four tetrahedral Si 4+ nearest to the Al 3+ tetrahedron. The most significant feature of the North Sea nano-quartz deduced in the present investigation is the presence of [4H] Si defects, also known as hydrogarnet...

...Taras L. Panikorovskii; Sergey V. Krivovichev; Evgeny V. Galuskin; Vladimir V Shilovskikh; Anton S. Mazur; Ayya V. Bazai Abstract Single crystals of Si-deficient vesuvianite with significant degree of hydrogarnet-type (SiO 4 ) 4− –(O 4 H 4 ) 4− substitution occur as epitactic overgrowth...

.... Initially formed hydrous stishovite is metastable and dehydrates over time in the low-temperature, high-pressure hydrothermal environment. The primary mechanism of H incorporation in stishovite is a direct substitution of 4H + for Si 4+ yielding unique octahedral hydrogarnet defects. In IR spectra...

... of Canada 2016 metamorphic-hydrothermal Ag-bornite Ag-paolovite argentopentlandite cassiterite chalcopyrite–lenaite Hg-silver mackinawite palladoarsenide parkerite Pd-breithauptite Sb-free paolovite silver Sn-hydrogarnet vincentite vysotskite The NOF is situated...

.... Calculations are performed within the primitive cell of cubic garnets. The hydrogarnet substitution, SiO 4 ↔ H 4 O 4 , yields 136 symmetry-independent configurations ranging from triclinic to cubic symmetry. All of them have been structurally optimized, the relaxed geometries being characterized by pseudo...

... groups are predicted to be bound to Si vacancies (□) as the hydrogarnet defect, [□ Si +4OH O ] X , at the Si2 tetrahedral site or as the [□ Mg +2OH O ] X defect at the octahedral Mg3 site. The hydrogarnet defect is more favorable than the [□ Mg +2OH O ] X defect by 0.8–1.4 eV/H at 20 GPa. The presence...

... incorporates significant hydroxyl into its tetrahedral structure (e.g. “hydrogarnet”; Rossman and Aines 1991 ; Grew et al. 2013 ). In this case, hydroxyl can reduce the symmetry of the usually isometric garnet, which changes its crystallographic properties from isotropic (black in transmitted light under...

... ones are continually being found. The compositional range is remarkable, as are the resulting chemical and physical properties. What are some of the compositions and their structures? The so-called hydrogarnets form a class of garnet where the central tetrahedrally coordinated Z cation is missing...

...-group mineral containing elevated concentrations of Nb (0.20 apfu , 13.33 wt.% Nb 2 O 5 ) and Ti (0.19 apfu Ti, 7.41 wt.% TiO 2 ), and evidence for the (SiO 4 ) 4− ↔ (OH) 4 4− “hydrogarnet” substitution. The crystal structure was solved and refined to R = 3.40% and wR 2 = 9.73% for 68 reflections with F...

.... A more extensive description of the mineral was offered by Marincea et al . (2001 , 2011 ), who gives chemical, crystallographic, and physical data. In many cases, the crystals of gehlenite from the exoskarn are embedded and partially engulfed by vesuvianite or hydrogarnet ( Fig. 1C ) as a result...

... include: (1) hydrogarnet and partial hydrogarnet-type substitution; (2) H-compensated trivalent substitution at the Si site; and (3) H-compensated trivalent substitution at the Zr site. The results provide a clear picture of the H locations in zircon and their associated IR stretching vibrations. Based...