In order to clarify inconsistencies in the literature and to verify assumed ternary solubilities, the phase equilibria in the Y2O3–Al2O3 –SiO2 system at 1600, 1400, and 1300 °C were experimentally determined using x-ray diffraction (XRD), scanning electron microscope with attached energy-dispersive detector system (SEM-EDX), and electron probe microanalyzer (EPMA). Six quasibinary phases were observed: Y4Al2O9 (YAM), YAlO3 (YAP), Y3Al5O12 (YAG), Y2SiO5, Y2Si2O7 (C and D modifications), and ˜3Al2O3· 2SiO2 (mullite). Y4Al2O9 forms an extended ternary solid solution with the formula Y4Al2(1-x)Si2xO9+x (x = 0 2 ˜0.31). The lowest ternary eutectic temperature was determined at 1371 ± 5 °C by high-temperature differential scanning calorimetry (DSC). The results were compared with previous data available for the Y2O3–Al2O3 –SiO2 system and with data for other RE2O3–Al2O3 –SiO2 (RE = rare earth element) systems.

Keywords:Zircon Xenotime Monazite Titanite Laser-induced REE photoluminescence Raman artefact Laser-induced photoluminescence of trivalent rare-earth elements (REEs), which is obtained as analytical artefacts in Raman spectra of selected accessory minerals, was studied. Spectra of natural titanite, monazite-(Ce), xenotime-(Y), and zircon samples from various geological environments were compared with emission spectra of synthetic, flux-grown analogues doped with REEs. The latter is of great importance to identify potentially mistakable bands as either Raman or PL signal, and to assign them to certain REE centres. In the samples investigated, various REE centres are excited selectively using 473, 514, 532, 633, and 785 nm laser excitation. Their assignment was verified by photoluminescence-excitation experiments. Luminescence spectral patterns of zircon and titanite vary in dependence of trace-REE concentrations, hence reflecting geochemical growth conditions. "REE artefacts" in Raman spectra of accessory minerals may be used as fingerprint tool for mineral phaseidentification. The distribution of REE emission-intensities, revealed by hyperspectral mapping, opens up the opportunity to visualise mineral textures, complementary to cathodoluminescence imaging-techniques.

Minamiite has been discredited and renamed natroalunite-2c to show a double unit-cell structure and natroalunite can be designated as natroalunite-1c to show a single unit-cell structure. Kintoreite can be designated as kintoreite-1c to show the same single unit-cell structure, and IMA 1993-039 is a new superstructure of kintoreite and can be designated as kintoreite-2c to show a double unit-cell structure. Beaverite has been renamed beaverite-(Cu). The Zn-bearing beaverite of Sato et al. (2008) has been named “beaverite-(Zn)”, but data for the mineralhave not been approved by the CNMNC. Orpheite has been discredited as P-rich hinsdalite. Proposal 07-D was approved by the CNMNC.

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The crystal structure of kröhnkite [Na

Dicaesium cobalt(II) dioxalate tetrahydrate [tetraaquabis("oxalato)cobalt(II)dicaesium(I)], Cs 2 Co II (C 2 O 4) 2 Á4H 2 O, has a layered structure and is isotypic with Cs 2 Mg(C 2 O 4) 2 Á4H 2 O. The unique Co atom shows octahedral coordination, with a mean CoÐO bond length of 2.084 A Ê. The Cs atom is irregularly coordinated by nine O atoms. Layers of CoO 4 (H 2 O) 2 octahedra, whose non-water O ligands belong to nearly planar bidentate oxalate groups, are separated by corrugated layers of Cs atoms. Medium-strong hydrogen bonds provide connections within the layer planes. All atoms are in general positions except the Co atom, which lies on a twofold axis. Comment As part of recent work on the crystal chemistry and topology of double metal oxalates (Kolitsch, 2004; Fleck & Kolitsch, 2004), the title compound has been prepared by crystallization from an aqueous solution at room temperature, and its crystal structure has been determined from single-crystal X-ray intensity data collected at 293 K. Cs 2 Co II (C 2 O 4) 2 Á4H 2 O is isotypic with Cs 2 Mg(C 2 O 4) 2 Á4H 2 O, the new structure type that was recently described by Kolitsch (2004). The title compound crystallizes in space group C2/c and exhibits a layered atomic arrangement. The asymmetric unit contains one unique Cs atom, one Co, two C, six O atoms and four H atoms. Only the Co atom is located on a special

A new occurrence of barysilite, PbxMn(Si207h, at the polymetallic Garpenberg Norra Zn-Pb deposit, Hedemora. Dalarna, Sweden, is described. The mineral, which forms colourless, transparent grains, is characterized by X-ray diffraction and electron-microprobe analyses. The assemblage includes tephroite, zincian jacobsite, manganoan diopside and others. The crystal structure of a barysilite crystal from Garpenberg Norra was redetermined using single-crystal X-ray diflraction data (Mo-Kex, CCO area detector) and has been refined in space group R3c with a = 9.804( I), c = 38.416(8) A, V = 3197.8(8) A', to RI = 2.32% for 1025 'observed' reflections with Fo >4a(Fo)' A previous, lowprecision structure determination (Lajzerowicz, 1965; R = 20%) is confirmed but improved considerably.The structure contains one dist011ed MnO(, polyhedron with six equivalent Mn-O bonds (2.224 A), one Si207 disilicate unit with an Si-O-Si angle of 120.9', and two non-equivalent Pb sites. The Pb I site has a highly irregular, one-sided coordination with six 0 ligands, indicating a stereoactive 6.1'2lone-electron pair on the Pb2-ion, whereas the [6+ 3]-coordinated Pb2 site is fairly regular, with Pb-O distances of 2.540 (3 x), 2.674 (3 x) and 3.098 (3 x ) A.. The Pb2 site contains -10% of Ca (+Ba) replacing Pb, corresponding to the structural formula Pb 16(Pb,Ca)22Mn(Si207h. This is the first direct proof that not only the M site in barysilite-type PbxM(Si207 h compounds can be replaced by divalent cations.