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 “Editor’s Notes” tab, which will be available shortly after the issue is live. 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, authenticate your login from the American Mineralogist website at http://www.msapubs.org/. On the portal page, click the 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 available to anyone who registers on the site. Thank you for reading American Mineralogist. Sincerely, Fabrizio Nestola Paul Tomascak Editors, American Mineralogist American Mineralogist Volume 111; Number 8; 08-01-2026 Single-crystal elasticity of celestine at ambient conditions Mark A. Johnson, Wenhao Su, Jia-Sen Hu, Jin S. Zhang This study reports the first full determination of single-crystal elastic properties of celestine (SrSO4). Using Brillouin spectroscopy, Johnson et al. resolved all nine elastic constants, clarifying large discrepancies in previous measurements. Comparison with baryte highlights the role of large cations in elastic anisotropy. These results provide benchmark data for sulfate minerals and inform methodological development for elasticity measurements. https://doi.org/10.2138/am-2025-10010 Geochemistry and structures of the exomorphic halo of the Volta Grande pegmatite, Brazil: Implications for net mass change and pegmatite emplacement Carlos F. Ávila, Ciro A. Ávila, Caymon S. Assumpção, Alexandre Lima, Tatiana Fedorenko, Antomat A. Macêdo FIlho, Maria Helena B.M. De Hollanda In this contribution, Ávila et al. have carried out geochemical and structural mass-balance analyses to quantify mass transfer between the Li-rich Volta Grande pegmatite and its host rocks. Their mass-balance calculations indicate that metasomatism transferred approximately 3–5 wt% K and 2 wt% Li from the pegmatite to the country rocks supporting open-system models in which pegmatite-forming fluids extensively exchange material with surrounding rocks. https://doi.org/10.2138/am-2025-10013 Quantitative analyses by combined energy- and wavelength-dispersive spectrometry: The best of both worlds Julien M. Allaz, Lukas Martin, Julian-Christopher Storck, Peter Ulmer, Eric Reusser, Razvan-Gabriel Popa, Arka Chatterjee, Olivier Bachmann This paper focuses on the ability of an EPMA or SEM equipped with energy- and wavelength-dispersive spectrometers (EDS, WDS) to use both detectors for standards-based quantitative X-ray analysis to yield precise and accurate compositions. Combined EDS-WDS analysis can be useful to reduce the analysis time, improve precision and accuracy, permit the post-analysis quantification of an element, etc. Standards-based EDS analysis can be equally as good as WDS, and Allaz et al. demonstrate it with examples in common Earth and planetary materials such as silicates, glasses, and apatite. https://doi.org/10.2138/am-2025-10014 A single-crystal neutron diffraction study of berborite-2T, Be2(BO3)(OH)·H2O G. Diego Gatta, Nicola Rotiroti, Geoffrey Bromiley, Jan C.M. de Hoog, Jörgen Langhof, Oscar Fabelo Berborite is one of the few minerals almost entirely composed of light elements (H, B, Be, and O), a feature that makes it an excellent target for neutron diffraction studies. By using EPMA-WDS, SIMS, single-crystal X-ray diffraction at 293 K, and neutron diffraction at 20 K, Gatta et al. reinvestigated the crystal chemistry of this mineral. Chemical and crystallographic data confirm the ideal formula of berborite as Be2(BO3)(OH)·H2O, with potential substituents (F, Cl, Na, K, Ca, Mg, Fe, and S) present only in negligible amounts. The structure of berborite-2T consists of two layers built from regular corner-sharing triangular BO3-units and tetrahedral BeO3Φ (Φ = OH, H2O) units, mutually connected to form electron-neutral [(BO3)Be2Φ2]-layers. The authors were able to describe in detail the complex H-bonding network based on neutron diffraction data. https://doi.org/10.2138/am-2025-10029 Haxonite, NiFe22C6, revisited: New crystal-chemical formulas and Fe-Ni ordering as a structure-stabilizing factor Oleg S. Vereshchagin, Liudmila A. Gorelova, Vladimir V. Shilovskih, Natalia S. Vlasenko, Renato Pagano, Sergey N. Britvin Vereshchagin et al. identify haxonite in Barbianello meteorite (iron ungrouped, Ni-rich ataxite). The Ni content in haxonite from the Barbianello meteorite is close to ~1.1 atoms per formula unit. The authors demonstrate that Ni orderly occupies a single crystallographic site. The dominance of Ni in a single crystallographic site also leads to the ideal formula of haxonite being NiFe22C6. Vereshchagin et al. hypothesize that the presence of Ni stabilizes haxonite crystal structure and makes haxonite common in Ni-rich irons. https://doi.org/10.2138/am-2025-10067 Vacancy ordering schemes govern the antiferromagnetism in a modulated pyrrhotite structure Alexander Firlus, Jürgen E.K. Schawe, Peter G. Weidler, Michael Wörle, Jörg F. Löffler, Andreas U. Gehring This study investigates how Fe-vacancy ordering influences the magnetic behavior of pyrrhotite. In this context, Firlus et al. Investigate a thermally tailored sample containing multiple vacancy-ordering variants exhibits two distinct vacancy-ordering schemes that control Fe-spin rotation. Thermomagnetic anomalies and secondary hysteresis loops provide evidence for two different spin-rotation mechanisms. These magnetic features are linked to structural distortions of Fe–Fe bonds associated with vacancy ordering. The results demonstrate that atomic-scale vacancy architecture plays a key role in determining the magnetic properties of pyrrhotite. https://doi.org/10.2138/am-2025-9847 Deep carbon cycling in subduction zones constrained by partial melting of phengite-bearing carbonated eclogite Yanfei Zhang, Chao Wang, Xiaoshu Hao, Penglei Liu, Fabin Pan, Zhenmin Jin The cycling of carbon from the subducting slab to the upper mantle wedge or arc magmas is important for understanding the variation of atmospheric CO2 concentrations. Zhang et al. use high-pressure and high-temperature experiments to study the decarbonation process of subducted eclogite with H2O stored in phengite. We find that dehydration of phengite can cause carbonate melting in subducted eclogite. This could improve the decarbonation efficiency of subducting crust and provide a source of carbon-rich liquids for mantle metamorphism and arc volcanoes. https://doi.org/10.2138/am-2025-9905 Chemistry of bridgmanite in the MgO-SiO2-Al2O3-FeO system at 27 GPa and 1700–2300 K Lucas Calvo, Artem Chanyshev, Fei Wang, Lin Wang, Takayuki Ishii, Catherine McCammon, Tomoo Katsura Earth's most abundant mineral, bridgmanite, comprises 75 vol% of the lower mantle. Changes in its chemical composition are a first-order explanation for the redox state of the mantle, volatile storage in the lower mantle, and mantle mixing. This study by Calvo et al. explores the solubility of diverse components in bridgmanite, finding enhanced vacancies compared to previous reports. https://doi.org/10.2138/am-2025-9935 Elasticity of silicate glasses along the MgSiO3-FeAlO3 join Jia-Sen Hu, Laura Schultz, Wenhao Su, Hongzhan Fei, Biao Wang, Wenyi Zhou, Tomoo Katsura, Jin S. Zhang Hu et al. investigated how Fe and Al affect the elastic properties of MgSiO₃–FeAlO₃ glasses, analogs for planetary magma ocean melts. Increasing FeAlO₃ content raises density and elastic moduli while reducing acoustic velocities. These compositional changes are expected to similarly influence silicate melts, with important implications for magma ocean evolution and planetary differentiation. https://doi.org/10.2138/am-2025-9982 Revealing the true nature of chrysocolla: From macro- to nano-characterization and first thermodynamic constraints Sara Monico, Roberto Conconi, Simone Tumiati, Andrea Bernasconi, Giancarlo Capitani, Ilaria Adamo, Loredana Prosperi, G. Diego Gatta, Petra Mácová, Radek Ševčík, Nicoletta Marinoni This study provides new insights into the mineralogy of chrysocolla through an integrated, multi-scale analytical approach. The combined use of complementary techniques reveals key aspects of its composition, short-range structural coherence, and nanostructure, which consists of an intricate network of randomly oriented nanotubes. These findings enhance our understanding of chrysocolla and have important implications for the evaluation of mineral and gemological resources. https://doi.org/10.2138/am-2025-9983 Predicting titanite genetic types from trace elements: A machine learning approach Dong Xie, Xue Gao, Runlong Fan, Junjie Han, Lei Ju, Kexin Li, Zengfeng Pan, Wenhang Teng, Liqiang Yang This study applies an interpretable machine-learning approach (LightGBM) to classify titanite according to its genetic origin using trace-element compositions. Based on more than 14,000 analyses, the model achieved 96% classification accuracy and was successfully validated on independent datasets. The approach proposed by Xie and coauthors in this study effectively distinguishes titanite from different geological settings, providing a robust tool for petrogenetic interpretation. https://doi.org/10.2138/am-2025-9987 Christine Elrod, Managing Editor (she.her.hers) ------------------------- American Mineralogist Mineralogical Society of America (MSA) Chantilly, VA 20151 editorial@minsocam.org<mailto:editorial@minsocam.org> Website: https://msaweb.org/MSA/AmMin/ FYI, Upcoming Out-of-Office Days and Holidays: Aug. 20-21; Sept. 3, 7