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, Hongwu Xu Paul Tomascak Fabrizio Nestola Editors, American Mineralogist American Mineralogist Volume 110; Number 12; 12-01-2025 Using multimodal X-ray computed tomography to advance 3D petrography: A non-destructive investigation of olivine inside a carbonaceous chondrite Matthew J. Pankhurst, Jette Oddershede, Rhian H. Jones, Daniel M. Thorley, Olivia A. Barbee, Nghia T. Vo, Katherine J. Dobson, Andrew Bodey, and David Eastwood Pankhurst et al. present a step-change in petrography/mineralogy towards full 3D, non-destructive analysis at the microscale. 3D data of rocks allows for true shape, size, and spatial characteristics and relationships to be measured and used to reveal patterns and trends between features and their 3D contexts that are impossible to see with 2D data. The grains' individual characteristics, like size and composition, can be individually inter-comparable, rather than populations with characteristics, like frequencies of composition or size distributions. https://doi.org/10.2138/am-2023-9213 Pre-eruptive characteristics of "suspect" silicic magmas in Carlin-type Au-forming systems Celestine N. Mercer, Julie Roberge, Regina M. Khoury, and Albert H. Hofstra World-class Carlin-type Au deposits formed when Eocene silicic magmas swept across Nevada in response to arc migration. Unlike other intrusion-related Au deposits, the origin of Carlin-type Au deposits remains controversial. In this study by Mercer et al., characterization of "suspect" magmas contemporaneous with these deposits yields a surprisingly broad compositional spectrum, suggesting a complex picture of silicic crustal magmatism during slab rollback. Carlin-type Au formation appears to be indifferent to this spectrum, implying that if magmas are involved, they perhaps do not need to be specialized. https://doi.org/10.2138/am-2024-9372 Formation and transformation of clay minerals influenced by biological weathering in a red soil profile in Yangtze River, China Yiming Wang, Qian Fang, Hanlie Hong, Lulu Zhao, Anbei Deng, Ke Yin, and Zhong-Qiang Chen Formation and transformation processes of clay minerals are influenced by both biotic and abiotic weathering, yet the specific mechanisms remain unclear. This investigation by Wang et al. reveals a profound association between biotic weathering involving organic acids and the formation and transformation of clay minerals. The findings underscore the significant influence of biotic weathering involving organic acids on the structure and composition of clay minerals, within the context of climate change, a phenomenon that is inadequately reported in natural systems, including soils and sediments. https://doi.org/10.2138/am-2024-9412 Mineralogy and precipitation control on saprolite lithium isotopes during intensive weathering of basalt Guanhong Zhu, Jinlong Ma, Gangjian Wei, Le Zhang, Wenfeng Deng, Xinyue He, and Zhuoying Zhang Understanding how Li isotopes respond to the changes in silicate weathering processes and climate is vital for reconstructing the weathering and climate history. Zhu et al. present Li isotope compositions of the saprolites and unaltered bedrock in a weathering profile developed on basalt in Hainan Island where abundant rainfall and the least dusty regions in China, and the δ7Li data from different rivers were compiled to decipher the dissolved δ7Li signatures. The results show that the effect of rainwater Li input on saprolite δ7Li values is indirectly by the adsorption and desorption of secondary minerals. Mineral control on saprolite Li isotopes yields distinct δ7Li values in the basaltic and granitic catchments. Diverse types of secondary minerals formed in the suspended load of the rivers may be another reason for the shifts in δ7Li values of rivers at different lithological regions. This work illustrates how precipitation affects the Li isotopic signatures of dissolved Li, thereby helping to decipher the seawater lithium isotope record over geological history. https://doi.org/10.2138/am-2024-9515 Anoxic and iron-rich seawater conditions facilitated reverse weathering: Evidence from the Mesoproterozoic siliceous rocks Zhutong Ke, Xiaoying Shi, Longfei Sun, Baozeng Xie, Jinxin Chen, Quan Zhong, Min Wang, Xinqiang Wang, Limin Zhou, Jianbai Ma, Lei Xu, and Dongjie Tang Ke et al. investigated authigenic berthierine and stilpnomelane in siliceous rocks of the Songziyuan Formation in South China. Petrographic and geochemical evidence indicate that silica-rich, anoxic, and iron-rich conditions facilitate the authigenesis of these minerals. Enhanced reverse weathering may have helped maintain the long-term greenhouse climate during the mid-Proterozoic. https://doi.org/10.2138/am-2024-9543 The effect of H2O on the crystallization of orthopyroxene in a high-Mg andesitic melt Lennart Koch, Renat R. Almeev, Stefan A. Linsler, Felix Marxer, and François Holtz Koch et al. experimentally investigated the crystallization behavior of orthopyroxene in a silicate melt at varying H2O concentrations and pressures. The results show that the crystallization temperature of orthopyroxene is depressed linearly with increasing water concentration in the melt. These findings can help improve current petrological models by providing a parameterization for the effect of H2O on crystallization temperatures of orthopyroxene. https://doi.org/10.2138/am-2024-9593 Apatite geochemistry records crustal anatexis: A case study of metapelites and granitic gneisses from the Cona area in the eastern Himalaya Min Ji, Xiao-Ying Gao, Cong Tu, and Xuan-Jin Chen Apatite, a common accessory mineral found in almost all types of metamorphic rocks, offers a valuable avenue for exploring its geological significance. Ji et al. investigated apatite in a series of metapelites and granitic gneisses that underwent amphibolite-to-granulite facies metamorphism in the Himalayan orogen. Apatite in these rocks exhibits distinct mineralogical features and major-trace element compositions. The results demonstrate that apatite geochemistry can effectively differentiate protolith type, metamorphic grade, and anatectic mechanism. By evaluating the mechanisms by which these factors influence the anatectic reaction, this study found that apatite can act as both a reactant and a product, with its geochemical composition serving as an indicator of the anatectic mechanism. https://doi.org/10.2138/am-2024-9685 Bradleyite Na3Mg(PO4)(CO3) inclusion in diamond, its structure and significance Felix V. Kaminsky, Enrico Mugnaioli, and Sofia Lorenzon Kaminsky et al. identified bradleyite Na3Mg(PO4)(CO3), a rare mineral, as an inclusion in a diamond. Since its discovery in 1941, the ab initio structure of bradleyite has been studied for the first time. The analysis of all known localities of bradleyite to date demonstrates that it is a polygenetic mineral, formed both in continental salt deposits under atmospheric pressure and in deep-formed igneous rocks, such as kimberlites and carbonatites, under high P-T conditions. The new finding of bradleyite demonstrates its stability in diamond-forming environmental conditions. https://doi.org/10.2138/am-2024-9704 Accurate XANES determination of microscale Fe redox state in clinopyroxene: a multivariate approach with polarization-dependent Fe K-edge XAFS Taisuke Ito, Simon R. Wallis, and Yoshio Takahashi Clinopyroxene shows significant variation in X-ray absorption depending on its crystallographic orientation relative to X-ray propagation and polarization. Ito et al. applied multivariate statistical techniques to determine microscale Fe2+/Fe3+ ratios irrespective of orientation with uncertainties of ±7.2–8.5%Fe3+ from X-ray absorption spectra. This result is a significant improvement on conventional methods (±13.5–15.3%Fe3+). The new method allows reliable measurements of Fe redox states using standard petrographic thin sections without destroying textures. https://doi.org/10.2138/am-2024-9712 Texture and geochemistry of multi-stage hydrothermal scheelite in the Dongyuan porphyry-type W-Mo deposit, South China: implications for the ore-forming process and fluid metasomatism Jia-Xiang Dong, Xiao-Fei Pan, Shao-Yong Jiang, Zeng-Qian Hou, Yan-Shen Yang, Suo-Fei Xiong, and Yong-Peng Ouyang The complex textures of minerals, such as scheelite, can yield crucial insights into fluid evolution history in ore deposits. Dong et al. employed optical microscopy, SEM-CL, EPMA, and LA-ICP-MS to analyze texturally complex scheelite, together with high-resolution fs-LA-MC-ICP-MS for sulfides coexisting with scheelite in the Dongyuan porphyry-type W-Mo deposit, South China. The analyses evaluate the origin, nature, and evolution of ore-forming fluids, the influence of surrounding rocks, and the formation mechanisms of different scheelite generations. Based on the results, the authors propose a model of host-rock interaction, assimilation, and the evolution of ore-forming fluids that contribute to W-Mo mineralization in the Dongyuan deposit. https://doi.org/10.2138/am-2024-9716 Revision of Y3+ ionic radii in common minerals based on trace element partitioning Matthew J. Kohn and Darin M. Schwartz The ionic radii of rare-earth elements (Sc, Y, and the lanthanides) are widely used for petrogenetic tracing as well as for thermometry. The accuracy of ionic radii underpins many applications. Kohn and Schwartz show that the ionic radius of trivalent Y is smaller than commonly assumed. Corrections improve thermometer accuracy by tens to hundreds of degrees. https://doi.org/10.2138/am-2025-9771 Aqueous fluid drives rhenium depletion in the continental crust Shuo Xue, Hongping He, Ming-Xing Ling, and Xing Ding This study resolves the long-standing mystery of rhenium (Re) depletion in the continental crust by demonstrating that post-magmatic fluid exsolution—not sulfide cumulation—dominates Re extraction. Shuo et al. show that Re partition coefficients between aqueous fluids and silicate melts scale systematically with H2O fugacity, revealing a fluid-driven depletion mechanism. During arc magma differentiation, approximately 80% of Re is scavenged by aqueous fluids, leaving the continental crust profoundly Re-depleted. These findings redefine our understanding of rhenium cycling in magmatic systems and underscore the critical role of fluid-mediated processes in shaping the geochemical architecture of the continental crust. The work also provides a quantitative framework for interpreting Re anomalies in arc lavas and ore-forming systems. https://doi.org/10.2138/am-2025-9774 Ertlite, NaAl3Al6(Si4B2O18)(BO3)3(OH)3O, a new mineral species of the tourmaline supergroup Jan Cempírek, Erik Jonsson, Lenka Skřápková, Radek Škoda, Uwe Kolitsch, Renata Čopjakova, Lee A. Groat, Anthony R. Kampf, Aaron J. Lussier, Frank C. Hawthorne, Jakub Haifler, Markéta Holá, and Martin Ende Cempírek et al. describe ertlite, the first tourmaline species in which boron replaces silicon at the tetrahedral site. The existence of the species has been anticipated since the late 1990s. Ertlite is defined using two tourmalines with the highest recorded tetrahedral boron contents to date. The discovery of ertlite allows recognition of its potential petrological importance in B-bearing sedimentary rocks, salar-type sedimentary sequences, or their low-grade metamorphic analogs. https://doi.org/10.2138/am-2025-9816 Synthesis and crystal structure of V-rich tourmaline Tatiana V. Setkova, Liudmila A. Gorelova, Oleg S. Vereshchagin, Anna V. Spivak, Polina A. Verchenko, Natalia S. Vlasenko, Vladimir N. Bocharov, and Dmitrii V. Pankin Setkova et al. investigated the newly formed overgrown layers of dark green tourmaline up to 0.7 mm in size with vanadium contents up to ~12 wt% V2O3 (~1.6 apfu) and ~41 wt% V2O3 (~6 apfu) for the systems (V1) V2O3-Al2O3-SiO2-B2O3-H2O and (V2) Na2O-MgO-V2O3-Al2O3-SiO2-B2O3-H2O, respectively. Synthetic tourmalines are triclinic (P1) due to cation orderings and could be considered as dimorphs of V-dominant analog of alumino-oxy-rossmanite (V1) and oxy-vanadium-dravite (V2). https://doi.org/10.2138/am-2025-9882 Synthesis of zircon-hafnon to determine oxygen isotope matrix effects in secondary ionization mass spectrometry Axel K. Schmitt, Leonid Aranovich, and Ilya Bindeman Oxygen isotopes in natural minerals carry important geochemical information, but variability at the micrometer scale requires high-resolution analytical techniques to extract it. This can be achieved using secondary ion mass spectrometry (SIMS), in which instrumental mass fractionation is corrected by comparison with a natural reference zircon. In this study, Schmitt et al. synthesized crystals with a wide range of Zr and Hf abundances to quantify how this compositional variation affects the accuracy of SIMS oxygen isotope data. The results demonstrate that Hf abundances in most natural zircon are uncritical relative to other uncertainty sources in SIMS oxygen isotope analysis, but conventional calibration introduces significant bias for Hf-rich zircon from pegmatites. https://doi.org/10.2138/am-2025-9886