September 2024 Paper Highlights Dear American Mineralogist Readers, Below are the Paper Highlights for this month’s issue of the American Mineralogist: International Journal of Earth and Planetary Materials. You may also view the American Mineralogist Paper Highlights list at https://msaweb.org/MSA/AmMin/ and click the far-right tab. The DOI links below will take you to the abstract on GeoScienceWorld. If you have “IP” access via your institution’s library, it should reveal the whole paper. Consult your institution’s IT department or friendly librarian. If you have an MSA membership, then authenticate from the American Mineralogist menu (here directly). Once at the portal page, click the right-side American Mineralogist link and enter your username (e-mail address) and your password (membership number). Then, search for the paper you want to read via your browser's search tools. (On most PCs, it is control-F, but that may vary for you.) Note that on GSW, you can sign up for a table of contents to be sent to you when the issue is live — this feature is open to anyone who registers on the site. Thank you for reading American Mineralogist. Sincerely, Hongwu Xu Don Baker Raman spectroscopy of the ilmenite–geikielite solid solution https://doi.org/10.2138/am-2023-9262 Ilmenite is an important mineral group for many planetary bodies, including the Earth, the Moon, and Mars. Breitenfeld et al. provide a model for estimating the Fe and Mg content of geologic samples within the ilmenite–geikielite solid solution series using Raman spectroscopy. This work is useful for laboratory analyses of terrestrial and extraterrestrial samples, real-time terrestrial fieldwork, or planetary surface exploration by astronauts. Germanium distribution in Mississippi Valley-Type systems from sulfide deposition to oxidative weathering: A perspective from Fule Pb-Zn(-Ge) deposit, South China https://doi.org/10.2138/am-2023-9106 Ge is crucial for high-tech industries, spurring considerable interest in studying its geochemical behavior in ore deposits. In this study, Wei et al. examine the Fule Pb-Zn(-Ge) MVT deposit in China as a typical case to reveal the partitioning of Ge between minerals and evaluate the mobility and redistribution of Ge during supergene weathering. A better understanding of Ge's distribution and mineral hosts in low-T hydrothermal systems have direct implications for Ge mobility and dictate metallurgical strategies for Ge recovery. Characterization and potential toxicity of asbestiform erionite from Gawler Downs, New Zealand https://doi.org/10.2138/am-2023-9184 Patel et al. describe the crystal chemistry of asbestiform erionite from Gawler Downs, New Zealand, for the first time. Complementary analytical methods were used to analyze the sample, including micro-Raman spectroscopy, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, electron microprobe analysis, and X-ray powder diffraction with the Rietveld method. The potential toxicity of the Gawler Downs erionite was computed, and results were comparable to that of other carcinogenic fibers such as fibrous erionite from Karain, Turkey (2.33) and Nevada, U.S.A. (2.28). First widespread occurrence of rare phosphate chladniite in a meteorite, winonaite Graves Nunataks (GRA) 12510: Implications for phosphide–phosphate redox buffered genesis in meteorites https://doi.org/10.2138/am-2023-9195 Anzures et al. describe the first widespread meteoritic occurrence of a rare Na-, Ca-, and Mg,Mn,Fe-bearing phosphate, chladniite, with numerous 1-500 µm chladniite grains found in winonaite GRA 12510, along with its first pure Raman spectrum. The calculated oxygen fugacity of this meteorite, along with other winonaites and IAB iron meteorites, falls along the P0-P5+ redox buffer. These results have implications for meteorite genesis, fast meteorite cooling rates, and new experimental techniques at oxygen fugacities between IW-2 and IW-4 that are important for primitive meteorite constituents (e.g., CAI's), partially differentiated planetesimals, planets including Mercury, and core formation on Earth. K isotopic fractionation in K-feldspar: Effects of mineral chemistry https://doi.org/10.2138/am-2023-9006 Liu et al. analyzed the stable K isotope compositions of 11 K-feldspar samples with varying degrees of Al/Si order, ranging from 0.22 to 0.94, and diverse lithological compositions. The δ41K values of these samples range from -0.710 to -0.075 ‰, which are trivially correlated with the degrees of Al/Si order. The correlations of δ41K with SiO2 and Al2O3 contents and the corresponding Al/Si mole ratios reveal that the K isotopic composition of K-feldspar is dependent on its Al and Si compositions. Its K isotopic fractionation may be insensitive to other factors, e.g., the source heterogeneity, which is further confirmed by comparing the δ41K values in this study with published δ41K values of K-feldspar from different sources. Jarosite formation in Permian-Triassic strata at Xiakou (South China): Implications for jarosite precipitation from H2S upwelling on Mars https://doi.org/10.2138/am-2023-9062 Hong et al. report the formation of sulfates, including jarosite, in K-bentonites within shallow-water facies of the Permian-Triassic (P-T) transition at Xiakou in South China. In these strata, jarosite is dispersed in the clay matrix or forms aggregates in pore spaces, has a euhedral morphology, and co-exists with variably 34S-depleted paragenetic gypsum and bassanite (δ34S = -37.23‰ to +3.20‰ VCDT). Subaqueous alteration of volcanic tuffs concurrently with oxidation of upwelled, biogenically sourced H2S is the process of jarosite formation in the Xiakou K-bentonites. This mechanism of jarosite precipitation and stability over geological time challenges the long-held view of acidic, water-limited conditions leading to iron(III) sulfate precipitation. It would be consistent with possible microbial or nanobial life on early Mars. The effect of A-site cations on charge-carrier mobility in Fe-rich amphiboles https://doi.org/10.2138/am-2023-9138 Bernardini et al. show that the A-site cations in Fe-rich amphiboles reduce the activation temperature of charge carriers, decrease the polaron dipole moment, slow down the process of re-localization of e-, and support the persistence of delocalized e- even at RT. The results have implications in Earth and materials sciences because they show that the A-site cations affect the depth of development of high conductivity in subducted amphibole-bearing rocks and demonstrate the potential of the amphibole-structure in designing functional materials with anisotropic-conductivity properties. Calorimetry and structural analysis of uranyl sulfates with rare topologies https://doi.org/10.2138/am-2023-9133 Five recently described uranyl sulfate minerals (lussierite, péligotite, shumwayite, geschieberite, and bluelizardite) were synthesized by Perry et al., their standard state enthalpy of formations determined with high-temperature calorimetry, and hydrogen positions found. The ΔHf° of péligotite was accurately estimated from the ΔHf° of lussierite and bluelizardite using literature ΔHf° values, suggesting the ΔHf° of other uranyl sulfate minerals can be accurately estimated. Biological control of ultra-skeleton mineralization in coral https://doi.org/10.2138/am-2023-9134 A combination of Raman spectral imaging and cross-polarized reflected light microscopy imaging was used by He et al. to reveal the three-dimensional spatial distribution, arrangement of skeletal ultrastructures and their associated mineral and organic compositions within coral, which has never been reported previously and will provide a new research paradigm for studies on biocarbonate microstructure and biomineralization process. These results will help to understand better the growth mechanisms of corals and their response and adaptation to global change. Systematic study of high field strength elements during liquid immiscibility between carbonatitic melt and silicate melt https://doi.org/10.2138/am-2023-9093 Zhang et al. conducted liquid immiscibility experiments to understand the changes in partition coefficients of Nb, Ta, Zr, and Hf between carbonatitic and silicate melts. The results showed a positive correlation between the partition coefficients of these elements and Si, indicating that Si determines the differentiation of Nb-Ta and Zr-Hf. The partition coefficients of Si increase as temperature decreases and pressure increases, resulting in higher HFSE concentrations during the early stages of liquid immiscibility. The study provides insights into the association between super large carbonatite-related Nb deposits and Si-undersaturated silicate rocks. Clustering and interfacial segregation of radiogenic Pb in a mineral host-inclusion system: Tracing two-stage Pb and trace element mobility in monazite inclusions in rutile https://doi.org/10.2138/am-2023-9085 Verberne et al. combine nanoscale microstructural and chemical analyses to gain insight into the relationship between Pb and trace-element systematics in monazite inclusions found in ultrahigh-temperature metamorphic rutile, specifically targeting the mineral-host–inclusion interface. . . Using techniques such as atom probe tomography and transmission electron microscopy, Verberne et al. characterize the rutile host, the monazite inclusion, and their shared interface. This allows the authors to constrain trace element systematics and derive the timing of metamorphism within the established P-T history by analyzing the Pb isotopic signature at interface. First application of scintillator-based photon-counting computed tomography to rock samples: Preliminary results and prospects https://doi.org/10.2138/am-2023-9099 Ishiguro et al. report the first results of applying a laboratory-built Photon Counting-Computed Tomography (PC-CT hereafter) system using a scintillator-based photon counter to minerals such as quartz and calcite. PC-CT uses a new type of energy-resolved X-ray detector, which allows X-rays with a continuous energy spectrum to be detected separately in arbitrary energy regions. The preliminary results suggest that PC-CT can produce high-contrast images of minerals and may be able to distinguish mineral phases with different attenuation curves, even when their CT values are similar. Moreover, if prior knowledge of mineral phases is given from other methods, it may be possible to use PC-CT imaging to obtain their chemical compositions. GCDkit.Mineral: A customizable, platform-independent R-language environment for recalculation, plotting, and classification of electron probe microanalyses of common rock-forming minerals https://doi.org/10.2138/am-2023-9032 Janoušek et al. present GCDkit.Mineral, a platform-independent (Windows/Mac/Linux) freeware for recalculation, plotting, and statistical treatment of mineral data obtained by microbeam techniques, typically an electron microprobe. Raw compositional data (wt%) are recalculated to atoms per formula unit (apfu) based on a required number of O equivalents, atoms, or charges, with or without FeII/FeIII estimation by a variety of methods. Analyses may then be recast to structural formulas, i.e., the atoms are distributed into appropriate crystallographic sites. For minerals forming solid solutions, the molar percentages of end-members are computed. All data may be treated statistically, either by built-in functions for descriptive and multivariate statistics or by using the wealth of tools provided by the broad R community. The program is fully menu-driven for users unfamiliar with R and contains embedded default recalculation options for many common rock-forming minerals. Seasoned R users may invoke GCDkit.Mineral in command line mode, use batch scripts or Python-driven notebooks (e.g., of project Jupyter), or modify and develop new recalculations or plugins. Apatite as an archive of pegmatite-forming processes: An example from the Berry-Havey pegmatite (Maine, U.S.A.) https://doi.org/10.2138/am-2023-9097 Roda-Robles et al. report a detailed petrographic and chemical characterization of apatite associated with the different units of a highly fractionated, internally zoned pegmatite that help understand the crystallization history of pegmatitic melts. Apatite chemistry records variations in the fO2, elemental fractionation, interaction with competing mineral phases, fluid activity, and exsolution events. The main chemical elements in apatite that provide petrogenetic information in pegmatitic rocks include Mn, Sr, REE, and Y. Re-examination of vesbine in vanadate-rich sublimate-related associations of Vesuvius (Italy): Mineralogical features and origin https://doi.org/10.2138/am-2023-9126 Pellino et al. give a detailed characterization of the V-bearing mineral assemblages on old vesbine samples from the Vesuvius volcano, kept in the Royal Mineralogical Museum of the University of Naples Federico II (Italy), a product of the fumarolic activity of Vesuvius volcano that is poorly understood. The purpose was to investigate the genesis of this peculiar assemblage. Temperature and compositional dependences of H2O solubility in majorite https://doi.org/10.2138/am-2023-9130 Liu et al. synthesized majorites with compositions, pressure, and temperature conditions relevant to the Earth's mantle and measured their H2O contents. They found that at the top lower mantle, where majorite persists beyond the stability of ringwoodite, majorite becomes the principal H2O reservoir. When a slab crosses the 660-km discontinuity, hydrous majorite transforms gradually into bridgmanite. This transformation may release water and contribute to a thick, hydrous melt-bearing layer below the 660-km discontinuity, up to ~800 km depth.