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 7; 07-01-2026 Colomeraite, NaTi3+Si2O6, a new clinopyroxene mineral from the Colomera iron meteorite Chi Ma and Alan E. Rubin Colomeraite is a new, high-temperature member of the jadeite subgroup under the pyroxene group. It is the first and only Ti3+-rich mineral identified in an iron meteorite. The name comes from the Colomera (Spain) iron meteorite. https://doi.org/10.2138/am-2025-10003 Dislocation density as a differential stress indicator in coesite and quartz: TEM constraints from shear experiments Jinyu Zheng, Tao Chen, Junfeng Zhang, Wenlong Liu, Feng Shi, Mingxing Gong, Zhe Gong This research focuses on the micro- to ultramicrostructural characteristics of shear-deformed coesite and quartz samples from experiments, which show similarities to the intergranular coesite and its retrograde quartz found in natural rocks. The authors employed EBSD, FIB, and TEM to analyze the micro- to ultramicrostructure of these shear-deformed samples, revealing their deformation behavior under varying high differential stresses. The results indicate that TEM is more effective than EBSD for exploring strong plastic deformation in these materials. Zheng et al. established power function relationships between dislocation density and differential stress for both coesite and quartz, providing a new method for estimating differential stress in UHP rocks. https://doi.org/10.2138/am-2025-10052 Impact-induced nano-sized rare mineral kuratite with correlated disorder on near and far sides of the Moon using 3DED method Yiping Yang, Jiaxin Xi, Haiyang Xian, Zhengyang Zhou, Shan Li, Zhi Li, Xiaoju Lin, Yuhuan Yuan, Huifang Xu, Jianxi Zhu, Hongping He, Yi-Gang Xu Mineral structures provide insights into how the Earth-Moon system formed and evolved. To address the problems intrinsic to micrometer-sized samples, new techniques (three-dimensional electron diffraction and advanced transmission electron microscopy) have emerged, allowing detailed study of tiny structures without needing large samples. In this research, Yang et al. found and analyzed a rare silicate mineral, kuratite, from lunar rocks collected by the Chang'e-5 and Chang'e-6 missions using these advanced methods. The study revealed complex, correlated disorder. The formation of kuratite and other special crystal structures (like dendrites and amorphous materials) are attributed to the melting and cooling processes caused by impact events on the Moon. This research enhances understanding of the differences between the Moon's near and far sides and could inspire new ways to create synthetic crystals with special properties for advanced materials. https://doi.org/10.2138/am-2025-9674 Determination of fluorine concentration in topaz using Raman spectroscopy Anselm Loges, Shilei Qiao, Xin Zhong, Jeremy Fuller, Timm John Quantification of fluorine in topaz has largely eluded conventional methods. Loges et al. present a quick and easy method for using Raman spectroscopy to determine the fluorine concentration in topaz. The method has the added advantages of being non-destructive and permitting high spatial resolution. https://doi.org/10.2138/am-2025-9785 Hydrogen incorporation in orthopyroxene from Southern Patagonian mantle xenoliths: The role of cooling upon emplacement Alexandra Demers-Roberge, Michael C. Jollands, Othmar Müntener Understanding mantle water content is crucial in petrology and rheological modeling, as even small amounts significantly affect the physical properties of rocks. Water content and OH– bonding environment details were determined in nominally anhydrous minerals from mantle xenoliths by FTIR . Four main defects in orthopyroxene have been experimentally confirmed, but natural mantle orthopyroxene spectra differ. Some experimental bands are absent, while new bands, like the key 3570 cm–1 peak, appear unassigned. Mantle xenolith samples from across the world show variability in the O-H stretching region (3000–3600 cm–1), potentially reflecting local or regional mantle processes. The authors investigate this variability using major and trace elements, and FTIR analyses of olivine, clinopyroxene, and orthopyroxene from eight localities on a transect representing snapshots of the mantle in the back-arc region in Southern Patagonia. The results show that variability in water contents and H-loss profiles reflect mantle water modification, re-equilibration with host magma, and H-loss during ascent or eruption. H-profiles in orthopyroxene reveal eruption-cooling timescales from minutes to hours, showing the potential of using frozen H-profiles in orthopyroxene to extract timescales and infer cooling mechanisms. https://doi.org/10.2138/am-2025-9798 Melt infiltration and redox heterogeneity in the upper mantle: Evidence from Fe-FeO-Fe3C assemblages in Luobusa chromitite (Southern Tibet) Fahui Xiong, Richard Wirth, Basem Zoheir, Yildirim Dilek, Xiangzhen Xu, Tian Qiu, Weibin Gui, Huidan Xie An unusual group of mantle minerals has been recently discovered in chromitite deposits in the Cretaceous ophiolite in Southern Tibet. Niobium-bearing minerals and silicate melt, Ti-rich magnetite, and wüstite that were incorporated into the peridotites in a molten state, along with Fe carbide and native Fe. The observed native Fe nitrides and Fe carboides were interpreted to have formed in the upper mantle, and not the transition zonoe, through the reaction of fluids or melt (rich in Ti and C) with magnetite, as a result of the infiltration of liquid metal. The study demonstrates the potential for reduced domains to persist in relatively more oxidized suprasubduction zone mantle. https://doi.org/10.2138/am-2025-9860 Local low-symmetry structure in iridescent garnet detected via spatially resolved electron diffractometry Yohei Igami, Akira Miyake, Yuhchyuan Chang, Norimasa Shimobayashi This study is a crystallographic characterization of a low-symmetry phase locally developed within an iridescent garnet from Tenkawa, Japan, using 4D-STEM. Using this spatially resolved electron diffractometry technique, Igami et al. found fine lamellae of Al-poor andradite and Al-rich regions with distinct symmetries. This finding contributes new structural insights into the andradite-grossular solid solution system, and the methodological advancement in this study can be applied to other complex mineral systems. https://doi.org/10.2138/am-2025-9870 Single-crystal X-ray diffraction of BaxCa1–xCO3 (0 ≤ x ≤ 0.79) solid solutions from 100 to 500 K: Implications for thermal expansivity of disordered calcite Yancheng Hu, Yu Ye, Dan Liu, Xi Zhu, Sha Wang, Yunfan Miao, Jiling Zhou, Zhen Wu, Yanming Pan CaCO3 plays a key role in global carbon cycling and is stabilized in aragonite and disordered calcite phases at lower and higher temperatures in the upper mantle. The thermoelastic properties of disordered calcite have not been achieved, since it cannot be quenched to the ambient condition. Solid solutions of BaxCa1–xCO3 are demonstrated to be successful ambient-stable analogs to investigate the thermal expansivity of disordered calcite by single-crystal XRD. The extrapolated volumetric thermal expansion coefficient for disordered calcite resembles that for aragonite. https://doi.org/10.2138/am-2025-9878 Graphitization of hydrogen-rich organic matter under high temperature and pressure Yuhui Wang, Suping Yao, Jian Cao, Xiaolin Wang, Yang Liu, Ning Zhu Wang et al. reveal that hydrogen-rich organic matter (HROM), when subjected to high pressures (0.5–3 GPa) and temperatures (up to 800 °C), transforms into nanocrystalline graphite and three-dimensional graphene foam through a distinct pathway marked by sp2 carbon enrichment and defect evolution. This transformation underscores the pivotal role of HROM in mediating lateral carbon layer growth, while lacking the vertical stacking efficiency observed in hydrogen-poor analogs. These results refine current models of deep carbon cycling and preservation, suggesting that incomplete graphitization of organic matter may persist to mantle depths. Beyond geoscience, the observed microstructural transitions offer a natural analog for engineering carbon-based materials with tunable crystallinity and porosity under extreme conditions, bridging Earth and materials sciences. https://doi.org/10.2138/am-2025-9883 Oxygen isotope and trace element mapping of growth and deformation of hematite single crystals from enriched banded iron formations Llyam White, Paulo M. Vasconcelos, Teresa Ubide, Janaina N. Ávila, Trevor R. Ireland White et al. present a combination of high-resolution analytical approaches based on in situ microbeam techniques that permit the determination of the trace-element composition, crystalline structure, and oxygen isotope composition of hematite crystals over time. The combination of analytical approaches identifies where the mineral started to grow, its crystallographic orientation or change of orientation during growth, and the changes in elemental and isotopic composition of the hematite crystal as it grew. https://doi.org/10.2138/am-2025-9900 Machine learning investigation of pyrite and chalcopyrite compositions to distinguish SEDEX and VMS deposits: An examination of the genesis of the Dongshengmiao deposit, Inner Mongolia, China Zhan Gao, Zhen-Jie Zhang, Yuan-Zhi Zhou, Qiu-Ming Cheng This study demonstrates the potential of machine learning to distinguish between SEDEX and VMS deposits by incorporating concentrations of key elements (e.g., Ni, Se, Sb, Pb) in chalcopyrite and pyrite into classification models. The model outperforms the traditional two-dimensional discriminant method and achieves a classification accuracy of 96–99%. This approach provides robust solutions for mineral resource assessment. For ancient sulfide deposits worldwide that are similar to Dongshengmiao, this study also provides new insights into primary mineralization processes obscured by subsequent metamorphism. However, since the classification models did not achieve 100% accuracy, there may still be some misclassified data points. Gao et al. recommend combining random forest, XGBoost, and multilayer perceptron classifiers and stacking to enhance model stability. https://doi.org/10.2138/am-2025-9907 Ultrahigh-pressure elasticity of dense hydrous SiO2 Yuichiro Mori, Motohiko Murakami, Takashi Yoshino, Hiroyuki Kagi Dense SiO2 phases such as stishovite and CaCl2-type SiO2 are the most elastically stiff minerals among major silicate and oxide minerals in the Earth's mantle. Those phases have a significantly large water solubility limit compared to the other nominally anhydrous minerals in the lower mantle constituent minerals. Mori et al. have made the first direct measurements of sound velocity on dense hydrous SiO2 from synthetic ultra-hydrous stishovite. The results showed that the shear wave velocity of SiO2 significantly decreases with water incorporation. The pressure dependence of stiffening of dense hydrous SiO2 could explain the elastically distinct region in the lower mantle. https://doi.org/10.2138/am-2025-9927 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: July 3, 17, virtual conference days: July 22-24; Aug. 20-21; Sept. 3