American Mineralogist November 2025 issue 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 “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 is a feature open 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 11; 11-01-2025 High-resolution analysis of clay minerals and amorphous materials in martian analog environments Michael T. Thorpe, Elizabeth B. Rampe, Juergen Thieme, Eric Dooryhee, Seungyeol Lee, and Roy Christoffersen Thorpe et al. document a combined high-resolution approach to better understand the nano-structure and composition of mud-sized sediments from a glacier- and river-fed watershed in southwest Iceland. Results demonstrate that sediments from the frigid climate of Iceland are more altered than previously thought and that the secondary amorphous assemblage is dynamic within the journey of sediment from the mountains to the ocean. On Earth, underestimating the extent of alteration in modern sediments has implications for interpreting the paleoclimate preserved in the geological record and for fully understanding the carbon cycle, as weathering can be a sink for CO2. This work emphasizes the importance of using high-resolution techniques for sample return missions, showing how the terrestrial reference frame can better interpret the sedimentary history of other rocky bodies. https://doi.org/10.2138/am-2023-9290 Nanoscale mapping of ZrSiO4 phases in naturally shocked zircon using electron energy loss spectroscopy Vladimir Roddatis, Elizaveta Kovaleva, Marcin D. Syczewski, Anja Schreiber, and Richard Wirth Roddatis et al. demonstrate a fast and reliable method to map a phase distribution of zircon and reidite in shocked zircon. The results were collected using EELS and verified with precession electron diffraction (PED). They describe differences in high- and low-loss spectra between zircon and reidite and demonstrate advantages of the method, such as very high spatial resolution and very short acquisition time, which can be applied to many other geological samples. This work presents important findings for mapping phases with identical chemical compositions (e.g., silicon oxides and calcium carbonates), whereas other methods are very time-consuming and have lower reliability. https://doi.org/10.2138/am-2024-9455 Nanogeochemistry of Ni, Co, and Cu in zoned marcasite-pyrite crystals Amira R. Ferreira, José María González-Jiménez, Lola Yesares, Idael F. Blanco-Quintero, Rubén Piña, and Fernando Gervilla This study investigates the micro-to-nanoscale features of zoned marcasite-pyrite crystals from the Sierra de Orihuela vein-type mineralization, revealing new insights into the partitioning of Ni, Co, and Cu during the formation of hydrothermal ore systems. The partitioning is attributed to solid solution and Ni-Co-Cu-rich nanoparticles. These findings highlight the economic potential of pyrite in ore deposits, emphasizing the importance of nanoscale studies in improving metal recovery. https://doi.org/10.2138/am-2024-9508 Native tin as solidified molten-metal droplets in a hydrothermal fluid from the epithermal Pukanec deposit (Slovakia) Juraj Majzlan, Ingo Horn, Stefan Weyer, Tomáš Mikuš, Jozef Vlasáč, and Adrián Biroň Metals are commonly transported as dissolved components in aqueous solutions. Majzlan et al. suggest that tin (Sn), as a metal with a low melting point, can also be transported as droplets of metallic melt and deposited with other, more common ore minerals. The findings, from metallic Sn droplets in a deeply weathered Au-Ag deposit, are supported by stable Sn isotope data and redox phase analysis. https://doi.org/10.2138/am-2024-9522 Genetic types of Zn-Pb deposits revealed by sphalerite geochemistry Qingwen Zeng, Qihai Shu, Qingfei Wang, Qian Zhang, Zhonghai Zhao, Xudong Niu, Fan Yu, Litian Zhang, and Jun Deng The identification of the genetic type of a mineral deposit, based on the compositional characteristics of specific minerals, is an important goal of economic geologists. Sphalerite often incorporates information from more than 10 elements, making it challenging to accurately represent the compositional nuances of these elements within traditional 2D diagrams. This study employs four extensively utilized machine learning algorithms to train 4908 sets of element data for sphalerite compiled from five distinct Zn-Pb deposit types. All the models exhibit satisfactory performance, achieving F1 scores that surpass 95%, which reflects the reliability of using sphalerite geochemistry to distinguish Zn-Pb mineralization types. The models from were used to classify three Zn-Pb deposits with unclear genetic types, with results consistent with geological observations. An Excel macro program was created to facilitate discrimination of the genetic type of Zn-Pb deposit. https://doi.org/10.2138/am-2024-9575 The transformation of magnesium phosphate minerals at atmospheric conditions: Mechanisms, kinetics, and environmental applications Rebecca Volkmann, Roberts Blukis, Christian Schmidt, Pablo Forjanes, and Liane G. Benning Struvite (MgNH4PO4·6H2O) is a mineral that precipitates from wastewater streams and blocks pipes. It was found that it can be recovered and manufactured into a phosphorus- and nitrogen-containing fertilizer used in agriculture, contributing to a sustainable phosphorus economy. However, struvite is unstable in air and decomposes into other minerals and phases; the speed and mechanisms of struvite transformation in air were tracked. It was found that struvite transforms into either newberyite (MgHPO4·3H2O) and/or dittmarite (MgNH4PO4·H2O), depending on the reaction temperature. This transformation changes the chemistry and hence the properties of the struvite fertilizer. https://doi.org/10.2138/am-2024-9578 High-energy resolution X-ray absorption spectroscopy study of the state of Pt in pyrite Olga Filimonova, Elena Bazarkina, Ruben Piña Garcia, Mauro Rovezzi, and Didier Wermeille Platinum replaces Fe in pyrite from the Ni-Cu-PGE Aguablanca ore deposit in a way equivalent to synthetically Pt-doped pyrite (identical Pt-S interatomic distances). The authors demonstrate this is not the effect of nano- or microinclusions. The "formal" oxidation state of isomorphous Pt in pyrite Fe2+S2 sample is close to +3.5. The partial atomic charge of isomorphous Pt in pyrite is close to +0.4. The covalent radii control the Pt incorporation into Fe sites of pyrite structure (ca. 3% different). The process of Pt-enrichment of pyrite sample took place at T > 360 °C. https://doi.org/10.2138/am-2024-9596 Contribution of Te-Bi melts in gold enrichment at the giant Jiaodong gold province, North China Craton: Insights from the Taishang deposit Zhong-Zheng Yuan, Zhan-Ke Li, Andrew G. Tomkins, Xiao-Ye Jin, Shao-Rui Zhao, Gao-Hua Fan, and Hua-Shan Sun Yuan et al. explore in detail the mineralogy and geochemistry of Au-Ag-Te-(Bi)-bearing phases and pyrite at the Taishang gold deposit to better understand the influence of Te-Bi melts in the gold enrichment and to refine the ore genesis models for the giant Jiaodong gold province. Te-Bi melts have been recognized as crucial agents for scavenging gold in magmatism-related gold deposits globally, often characterized by a notable Au-Te-Bi association. This association is also recognized in gold deposits of the Jiaodong district, though the specific roles of Te and Bi in gold enrichment here have not been thoroughly evaluated until now. The mineralogical patterns reveal a strong relationship between Au, Ag, Te, and Bi, corroborated by trace element compositions of pyrite, which exhibit strong positive correlations among these elements. Furthermore, the texture of Au-Ag-Te-(Bi) assemblages in Stage I and II (i.e., unsharp and curvilinear boundaries) suggests crystallization from melts. Supported by relevant experimental evidence, the low melting points of Au-Ag-Te-Bi systems enable Te-Bi melts to effectively scavenge gold from fluids at the temperature conditions of Taishang. The presence of Au-Ag-Te-Bi association in both Taishang and other Jiaodong gold deposits underscores the importance of Te-Bi melts in enhancing gold enrichment. https://doi.org/10.2138/am-2024-9597 Origin and evolution of granitic pegmatite rare metal deposits in the northern Mufushan batholith, South China: Insights from muscovite chemistry Shuai Zheng, Jian-Hui Su, Jian Wang, Shuai-Jie Liu, and Xin-Fu Zhao Granite pegmatites are generally considered to be the final products of the differentiation of the continental crust and are an important source of incompatible rare metal elements. However, the origin of granite pegmatites and the enrichment mechanism of rare metals remain a subject of debate. In this study, Zheng et al. focus on the coeval, cogenetic barren and rare metal pegmatites as well as the associated granitic intrusions in the northern Mufushan batholith in South China. Overlapping initial εNd(t) permits the pegmatite groups to be related. The authors calculated the initial melt compositions in equilibrium with muscovite for both types of pegmatites. The results show that pegmatites may represent distinct degrees of Rayleigh fractionation (from 50 to 90%) with constitutional zone refinement. These findings may be widely applied to granite pegmatites worldwide. https://doi.org/10.2138/am-2024-9636 Wangyanite, PdNi8S8, a new Pd end-member mineral of the pentlandite group from the J-M reef, Stillwater Complex, Montana, U.S.A. Chen Chen, Haiyang Xian, M. Christopher Jenkins, Zhuosen Yao, Yiping Yang, Xiaoju Lin, Shan Li, Jiaxin Xi, Yuhuan Yuan, Jianxi Zhu, and Hongping He The behavior of platinum-group elements (PGE) in magmatic processes is critical for understanding the formation of PGE-rich deposits in mafic-ultramafic intrusions. The classical theory indicated that pentlandite exsolved from monosulfide solid solution (MSS) contains only low concentrations (ppb-ppm) of Pd. However, the enrichment of Pd in pentlandite, ranging from hundreds ppm to a few wt%, is widely observed in nature and unexplained by the classical theory. In this contribution, Chen et al. found a new Pd-dominant mineral, wangyanite, PdNi8S8, having an average Pd content of 9.95 wt%, from the J-M reef of the Stillwater complex. The authors identify this mineral, which has been approved by the IMA-CNMNC, as the Pd-member of pentlandite group. Although wangyanite shares the same crystal structure with pentlandite, the octahedrally coordinated site in wangyanite is mainly occupied by Pd, but not the Ni and Fe. Based on textural features, wangyanite is suggested to be formed by peritectic reaction between braggite, pentlandite, and sulfide liquid, which matches experimental results from the Pd-Fe-Ni-S phase system. The authors believe that the discovery of wangyanite can push geologists into rethinking the formation mechanism of Pd-rich pentlandite and its relationship to PGE minerals and base metal sulfides during the cooling and evolution of sulfide melt. https://doi.org/10.2138/am-2024-9640 In situ observation of the subsolidus reactions between petalite and spodumene + quartz in a hydrothermal diamond-anvil cell Qiang Liu, Jiankang Li, Yongchao Liu, and Peng Li Spodumene and petalite are the primary minerals mined from pegmatites, the most important sources of hard-rock Li resources. In Li-mineralized pegmatites, the subsolidus reaction of petalite → spodumene + 2 quartz (reaction 1) and its reverse reaction, spodumene + 2 quartz → petalite (reaction 2), produce secondary spodumene, usually in the form of spodumene and quartz intergrowths (SQI), and secondary petalite, respectively. The experimental results of reaction 1, including reaction 2, can be applied to estimate reaction rates and corresponding growth rates under specific P-T conditions, aiding in the analysis of the morphology and origin of secondary spodumene and SQI in pegmatites. Combined with the P-T fields of Li-aluminosilicate minerals in the LiAlSiO4-SiO2-H2O system, these results can further constrain the P-T paths of pegmatite formation. Similarly, the reaction 2 parameters obtained in the experiments can be used to assess the origin of secondary petalite and constrain pegmatite P-T paths. https://doi.org/10.2138/am-2024-9652 Crystal chemistry and high-temperature behavior of Al-bearing stishovite and Al-rich phase D: Implications for water storage in the deep mantle Li Zhang, Joseph R. Smyth, and Chaowen Xu Water (hydrogen) plays a critical role in controlling the evolution and dynamics of the Earth's interior. It is widely believed that the subducting slab serves as an effective carrier for transporting both H and Al from surface environments to the lower mantle. However, the structural characteristics, water contents, and thermal stabilities of nominally hydrous and anhydrous phases in Al-rich regions of the deep mantle remain poorly constrained. Zhang et al. analyzed high-quality single-crystal samples of Al-bearing stishovite and Al-rich phase D by using X-ray diffraction, high-temperature Raman, and FTIR analyses. Crystals were synthesized at 25 GPa, 1350–1600 °C in the MgO-SiO2-Al2O3-H2O system. The experimental results demonstrate that Al-rich silicate glass and Al-bearing SiO2 glass, formed respectively by the temperature-induced amorphization of phase D and stishovite, can retain water in the form of hydroxyl groups. This implies that Al-rich silicate glasses and Al-bearing SiO2 glasses may serve as potential reservoirs of H in the lower mantle and participate in deep water cycling processes in the Earth's interior. https://doi.org/10.2138/am-2024-9665 Nb-Ta mineralization in a metaluminous-weakly peraluminous magmatic system: Constraints from the chemical compositions and Hf isotopes of columbite-group minerals in China Zhi-Min Tang, Xu Dong Che, Ru Cheng Wang, Yueheng Yang, Fuyuan Wu, Robert Linnen, Fei Deng, Huan Hu, Jian-Jun Lu The sources of Nb-Ta deposits associated with metaluminous-weakly peraluminous (MWP) and strongly peraluminous systems exhibit differences. In the MWP system, Nb mineralization is primarily controlled by Nb-enriched sources. Despite relatively low degrees of magma evolution, this enrichment can effectively reduce the dependence on extreme fractional crystallization, allowing Nb to concentrate to saturation levels, ultimately leading to mineralization. The Nb-Ta mineralization in South China during the Early Cretaceous (~140–120 Ma), associated with MWP systems, is attributed to contributions from a deep material source within an extensional tectonic setting. https://doi.org/10.2138/am-2024-9668 Structural behavior and magnetic properties of coquimbite AlFe3(3+)(SO4)6(H2O)12·6H2O over a wide temperature range Veronika Abdulina, Artem Borisov, Oleg Siidra, Victoria Ginga, Nicolas Sanchez, Annette Setzer, Astrid Holzheid Understanding the stability of hydrated sulfates and establishing their existence under a wide range of temperatures is crucial for various scientific and technological applications. Abdulina et al. present a comprehensive study of the thermal and magnetic behavior of coquimbite over a wide temperature range and low vacuum (600 Pa). The behavior of coquimbite with increasing temperature can be divided into two stages: (1) negative and strongly anisotropic thermal expansion; (2) positive thermal expansion. Magnetic properties are driven by antiferromagnetic interactions within its M3-M2-M3 trimeric clusters of Fe3+. https://doi.org/10.2138/am-2025-9776