American Mineralogist February 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.
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Thank you for reading American Mineralogist.
Sincerely,
Hongwu Xu
Paul Tomascak
Editors, American Mineralogist
American Mineralogist
Volume 110; Number 2; 02-01-2025
Quartz textures, trace elements, fluid inclusions, and in situ oxygen isotopes from Aktogai porphyry Cu deposit, Kazakhstan
Changhao Li, Ping Shen, Reimar Seltmann, Di Zhang, Hongdi Pan, and Eleonora Seitmuratova
Two types of magmatic quartz and nine types of hydrothermal quartz are identified in the Aktogai porphyry Cu deposit. Mineralizing fluids at Aktogai underwent fluid immiscibility, mixing, and cooling. Copper precipitation at Aktogai is caused by fluid cooling and water-rock reactions. This work demonstrates that Ti-in-quartz thermobarometry is a useful tool for estimating the emplacement depths of ore-related intrusions.
https://doi.org/10.2138/am-2023-8931
Cu nanoparticle geometry as the key to bicolor behavior in Oregon sunstones: An application of LSPR theory in nanomineralogy
Chengsi Wang, Andy H. Shen, Peter J. Heaney, Aaron Palke, Ke Wang, Haiying Wang, and Lore Kiefert
Oregon sunstone is a well-known gem whose color mechanism cannot be explained by classical mineral coloration theories. Wang et al. employed focused ion beam extraction and high-angle annular dark-field scanning transmission electron microscopy to document the presence of Cu nanoparticles in Oregon sunstones. The nanoparticles occurred as two distinct morphological populations. Spherical nanoparticles measuring ~10 nm in diameter were associated with red isotropic zones. Nanorods up to ~20 nm in length occurred in anisotropic zones that exhibited green and red coloration. This study successfully applied localized surface plasmon resonance (LSPR) theory to simulate absorption spectra for the isotropic and anisotropic zones of Oregon sunstones, confirming that variably shaped Cu-nanoparticles in feldspar crystals control the optical behavior of these gems.
https://doi.org/10.2138/am-2023-9141
Oriented triphylite rods in apatite from an LCT pegmatite in the Stankuvatske Li-ore deposit, Ukraine: Implications for Li mobility
Sergii Kurylo, Igor Broska, and Gieré Reto
Kurylo et al. report the first finding of oriented triphylite rods in greenish-blue fluorapatite in the apatite zone of the contact between a metamorphosed rare-metal pegmatite and its amphibolite wall rock at the Stankuvatske Li-ore deposit (Ukrainian Shield). The needle-shaped triphylite inclusions are oriented parallel to structural nanochannels along the c-axis in apatite. The inclusions were formed within apatite due to the interaction between pegmatite-derived Li-rich fluids and components derived from the wall-rock amphibolite. The apatite zone in the endocontact acts as a geochemical barrier to the further escape of Li from the pegmatite and thus might have been responsible for the accumulation of important rare metals, such as Li, Rb, Cs, Nb, Ta, and Sn. Therefore, the presence of an apatite geochemical barrier may even be used as a prospecting tool for rare metals in other pegmatites around the world.
https://doi.org/10.2138/am-2023-9172
Role of impurities in the semiconducting properties of natural pyrite: Implications for the electrochemical accumulation of visible gold and formation of hydrothermal gold deposits
Baisong Du, Jun Deng, M. Santosh, Zuoman Wang, Yuke Shen, Shufei Liu, Hanwen Yang, and Kexin Xu
Du et al. used in situ Seebeck coefficient and thermoelectric measurements, as well as trace element geochemistry to investigate the enrichment mechanism of gold in pyrite. The compositional heterogeneity of impurities dissolved in pyrite affects the semiconducting properties of pyrite. Electrical p-n junctions can result in the electrochemical precipitation of visible gold. The electrochemical precipitation mechanism of gold may also account for the formation of other types of hydrothermal gold deposits.
https://doi.org/10.2138/am-2023-9187
A simple method to create mineral mounts in thin section for teaching optical mineralogy
Matthew J. Kohn
Kohn provides step-by-step instructions for creating grain mounts in thin sections. This method teaches the optical properties of minerals, specifically color/pleochroism, relief, and birefringence. It also allows the mounting of fragile materials.
https://doi.org/10.2138/am-2023-9285
Unraveling clay-mineral genesis and climate change on Earth and Mars using machine learning-based VNIR spectral modeling
Lulu Zhao, Anbei Deng, Hanlie Hong, Jiannan Zhao, Thomas J. Algeo, Fuxing Liu, Nanmujia Luozhui, and Qian Fang
Hydrated silicate minerals are common in martian geological units and are globally widespread. Understanding the formation and evolution of clay minerals is pivotal in uncovering the environmental conditions of early Mars. Zhao et al. collected soil/sediment samples from five different climatic zones to elucidate the degree of crystallinity and clay-mineral alteration process related to climatic conditions. The results show that VNIR spectral modeling has the potential to unveil genetic and climatic information at both field and regional scales. This study has significant implications for space exploration, notably for missions to Mars.
https://doi.org/10.2138/am-2023-9299
Uramphite, (NH4)(UO2)(PO4)·3H2O, from the second world occurrence, Beshtau uranium deposit, Northern Caucasus, Russia: Crystal-structure refinement, infrared spectroscopy, and relation to uramarsite
Vladislav V. Gurzhiy, Anatoly V. Kasatkin, Nikita V. Chukanov, and Jakub Plášil
Gurzhiy et al. report the discovery of uramphite, (NH4)(UO2)(PO4) · 3H2O, at Beshtau uranium deposit, Northern Caucasus, Russia. They conducted structural refinement using single-crystal X-ray diffraction data and proposed a model for the distribution of H2O and NH4+ molecules in the interlayer space. IR spectrum shows the splitting of the band of H–N–H bending vibrations into four components, which is explained by the resonance splitting of a group of NH4+ cations occurring around the four-fold axis at close distances from each other. Although uramphite is related to uramarsite, (NH4)(UO2)(AsO4)·3H2O, they are not isostructural. Uramarsite is triclinic, contains a significant amount of P in arsenate sites, and significantly differs from uramphite by the arrangement of H2O and NH4+ molecules in the interlayer space. Bacterial activity might be crucial for the formation of both uramphite and uramarsite at Beshtau uranium deposit.
https://doi.org/10.2138/am-2024-9313
Al3+ and H+ substitutions in TiO2 polymorphs: Structural and vibrational investigations
Sha Wang, Qingbo Wang, Yu Ye, Dan Liu, Xi Zhu, Yancheng Hu, Yunfan Miao, Zhen Wu, and Yanming Pan
The coupled substitution of Ti4+ = Al3+ + H+ is identified in the α-PbO2 type TiO2 polymorph, and its water solubility is much higher than those in CaCl2- or rutile-type phases, making it an important water carrier in the mantle transition zone and lower mantle, when coexisting with trivalent cations. A negative linear correlation is drawn between the measured OH stretching frequencies and the theoretically calculated local M3+O6 quadratic elongation among TiO2 and SiO2 polymorphs.
https://doi.org/10.2138/am-2024-9316
Gender in mineral names
Christopher Emproto, Gabriela A. Farfan, Tyler L. Spano, Marko Bermanec, Mike S. Rumsey, Barbara L. Dutrow, Raquel Alonso-Perez, Jessica Riaño, and Adam C. Simon
Emproto et al. compiled the name information for 5901 minerals to evaluate how mineral naming trends have changed over time, focusing on gender among people with minerals named for them. More than half of all minerals are named for people, roughly 94% of whom are men. Projections indicate that women will never be equally represented among new mineral namesakes. Additional analyses highlighted age and nationality discrepancies that enumerate the lack of women in the mineral sciences.
https://doi.org/10.2138/am-2024-9327
Zhonghongite, Cu29(As,Sb)12S33, a new mineral from the high-sulfidation vein of Jiama porphyry system, Tibet, China
Shi-Ji Zheng, Xiang-Ping Gu, Zhong-Jie Bai, and Zhong-Kun Zhang
Zheng et al. report the discovery of zhonghongite, Cu29(As,Sb)12S33, a new mineral from the later high-sulfidation vein of the Jiama mine. They determined its optical characteristics, chemical composition, and crystal structure. Zhonghongite, watanabeite, and tennantite-tetrahedrite are closely intergrown and share the same major elements: Cu, As, Sb, and S. The authors compare the structural characteristics of zhonghongite to tennantite, which exhibits a similar crystal structure, but zhonghongite is more complex, with five As(Sb) sites in the structure.
https://doi.org/10.2138/am-2024-9338
Gowerite, Ca[B5O8(OH)][B(OH)3]·3H2O: Revisiting the crystal structure and exploring its formation context
Atsushi Kyono and Kosuke Yamaguchi
Kyono and Yamaguchi investigated the structural characteristics and formation environment of gowerite. Hydrothermal experiments resulted in the successful synthesis of gowerite. The study delves into the molecular orbitals, highlighting the spatial distribution and strong covalent bonds within the unique fundamental building blocks, and examines the structural inheritance of FBBs during phase changes. This work enhances our understanding of borate mineral formation and characteristics, contributing valuable insights to borate mineralization studies.
https://doi.org/10.2138/am-2024-9367
Characteristics of the distribution of minerals among the space groups
Carl N. Drummond and Princess N. Sarpong
It is recognized that minerals are non-uniformly distributed among the space groups and their corresponding point groups and crystal systems. This non-uniformity is not non-systematic. A series of relationships that collectively characterize crystallographic controls on and resultant distributions of mineral occurrence among the crystallographic space groups has been identified.
https://doi.org/10.2138/am-2024-9381