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Perovskite mineral oxides commonly exhibit extensive solid-solution, and are therefore classified on the basis of the proportions of their ideal end-members. A uniform sequence of calculation of the end-members is required if comparisons are to be made between different sets of analytical data. A Microsoft Excel spreadsheet has been programmed to assist with the classification and depiction of the minerals of the perovskite- and vapnikite-subgroups following the 2017 nomenclature of the perovskite supergroup recommended by the International Mineralogical Association (IMA). Compositional data for up to 36 elements are input into the spreadsheet as oxides in weight percent. For each analysis, the output includes the formula, the normalized proportions of 15 end-members, and the percentage of cations which cannot be assigned to those end-members. The data are automatically plotted onto the ternary and quaternary diagrams recommended by the IMA for depiction of perovskite compositions. Up to 200 analyses can be entered into the spreadsheet, which is accompanied by data calculated for 140 perovskite compositions compiled from the literature. [ABSTRACT FROM AUTHOR]

Abstract: A Microsoft Excel spreadsheet has been programmed to assist with classification of chemical analyses of orthorhombic and monoclinic amphiboles following the 2012 nomenclature recommended by the International Mineralogical Association. The spreadsheet is intended for use only with compositional data (wt% oxides and halogens, rather than atomic proportions) and provides options for the estimation of Fe3+/ΣFe and Mn3+/ΣMn ratios and OH content. Various cation normalization schemes can be automatically or manually selected. For each analysis, the output includes the group, subgroup (or B-occupancy for the oxo-amphiboles), and species name including any mandatory chemical prefixes, along with a formula based on 24 anions. The formula results can be exported in a form suitable for the AMPH2012 program. Prefixes related to space groups (proto-) and suffixes (–P21/m) are not assigned in the spreadsheet. Large data sets (up to 200 analyses at a time) can be accommodated by the spreadsheet, which is accompanied by results calculated for more than 650 amphibole analyses taken from the literature. [Copyright &y& Elsevier]

A Microsoft Excel spreadsheet has been programmed that allows users to calculate with ease the molar proportions of garnet end-members from chemical analyses. Recent advances in the understanding of the crystal chemistry of natural garnets, especially of the Ti-bearing garnets, are used to evaluate 29 end-members (15 species and 14 hypothetical end-members) for each analysis. The amounts of Fe2+ and Fe3+ (and Mn3+, if necessary) are calculated by stoichiometric constraints if these quantities have not been measured. The input data can include: SiO2, TiO2, ZrO2, SnO2, Y2O3, Al2O3, Sc2O3, Cr2O3, V2O3, FeO, Fe2O3, MnO, MgO, CaO, Na2O, H2O+ and F. The spreadsheet can be used with large data sets (up to 100 analyses at a time), and is accompanied by results calculated for 470 garnet analyses taken from the literature. The spreadsheet employs a simple scoring algorithm to measure the quality of a garnet analysis. The propagation of error from the input chemical data to the calculation of end-member proportions is also discussed briefly. [Copyright &y& Elsevier]

Abstract: Infrared (IR) spectra of phases found in calcium-aluminum rich inclusions in meteorites are incomplete, yet such data are needed to ascertain the mineralogy of astronomical environments. To better characterize the system CaO-Al2O3, we obtained IR thin-film absorption data, partially polarized Raman scattering spectra, and single-crystal X-ray structure refinements from small single-crystals of end-member hibonite (CaAl12O19) and grossite (CaAl4O7), synthesized by laser-heating. Vibrational spectra were also acquired from natural samples of Th-bearing hibonite, synthetic corundum (Al2O3), 17O-enriched grossite, CaAl2O4, and CaO. Spectral fitting provided band positions and widths. The true absorbance of strong IR peaks in calcium aluminates is 1–2/μm, based on thickness determined from interference fringes and on comparison with absorption coefficients calculated from reflectivity data on natural hibonite. Our data on the lattice vibrations of hibonite reveal that the terrestrial samples are partially metamict: their spectra cannot be used for comparison with astronomical objects because of peak broadening and changes in the polarization of the vibrations. Direct comparison of our IR data of synthetic samples with astronomical observations shows that grossite and hibonite are present in the proto-planetary nebula NGC 6302. That spectral patterns match provides a strong case. Corundum, spinel, and melilite-group minerals also could be present in the nebula. Because spectra of melilites resemble those of pyroxenes, the latter assignment is less certain. We limit our compositional analysis of the nebula to matching spectral patterns, because detailed spectral modeling of the mineralogy would be both premature (due to a lack of cryogenic IR data), and uncertain (due to the occurrence of dust in clumps large enough to emit as blackbodies). The inferred mineralogy of NGC 6302 follows the condensation sequence for a nebula of solar composition, and contains mineral types known to be presolar. [Copyright &y& Elsevier]