Volume 110, Issue 2

Minerals are the fundamental constituents of Earth, and mineral names appear in scientific literature for disciplines including geology, chemistry, materials science, biology, and medicine, among others. Choosing a name is the full responsibility of the authors of new mineral proposals submitted to the International Mineralogical Association (IMA). Scientific nomenclature and its traditions have evolved over time, and consequently, mineral names track changes in the landscape of mineralogy with respect to language, technology, and culture. To evaluate these changes, the namesake information for all 5896 minerals approved by the IMA or “grandfathered” into use as of December 2022 was recorded and categorized within a workable database. The compiled information yields diverse insights into the intersection of science and culture and could also be used to project future trends. In this study, we used the name database to investigate gender diversity among mineral eponyms. More than half (ca. 54%) of all mineral species are named after people, the identities of whom are largely a reflection of the people that have historically been involved, in one way or another, in the geosciences and the mining industry. Of the 2738 people with minerals named for them, ∼6.1% are (interpreted to be) women. Nearly all minerals named for women were named during the last 60 years, although the growth rate in the year-on-year percentage of women among new mineral namesakes has slowed since about 1985. If current and historical trends hold, our model predicts that women will not comprise more than about 10.35% of newly established mineral namesakes in future years. The representation of women among mineral namesakes also differs starkly among countries. For example, Russians comprise 43.11% of women with minerals named for them but account for only 15.12% of all eponyms. However, there are additional disparities beyond the proportions of namesakes. For scientists who were alive when a mineral was named for them, women averaged 3.74 years older than men when evaluated over the same timespan (1954–2022). These results demonstrate that gender-based disparities are imprinted into current mineral nomenclature and indicate that gender parity among new mineral namesakes is impossible without unprecedented changes in the upstream demographics that are most likely to affect naming trends.

Pyrite (FeS 2 ), the most abundant sulfide mineral on Earth, typically contains a host of minor and trace elements, including As, Co, Ni, and Au. It is an important semiconductor with unique structural properties markedly influenced by elemental impurities. However, whether the change in semiconducting properties of natural pyrite is caused by the type and concentration of trace elements or by a non-stoichiometry-related doping mechanism remains uncertain. Moreover, the effect of semiconducting properties on the enrichment mechanism of Au has not been well addressed. Here, we investigate microscopic pyrite crystals from the Heilangou gold field (HGF) in the eastern Jiaodong Peninsula using field emission scanning electron microscopy (SEM), electron probe microanalysis (EPMA), in situ laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), potential-Seebeck microprobe (PSM), and thermoelectric measurements. The results demonstrate that pyrite grains show either p- or n-type conductivity depending on chemical compositions. Pyrite enriched in As, which typically substitutes for S in the crystal structure, tends to be p-type with a positive Seebeck coefficient, whereas pyrite crystals enriched in Co, Ni, Cu, and Zn, as well as those depleted in As, are typically n-type. Moreover, As shows the strongest influence on the semiconducting properties of natural pyrite crystals and a strong positive correlation with Au. We observed that visible Au grains are preferentially accumulated on individual domains of sulfides (e.g., As-rich pyrite) that act as cathodes, suggesting that electrical p-n junctions in sulfides drive electrochemical reactions with ore-forming fluids, resulting in the deposition of visible Au. The electrochemical precipitation mechanism of Aumay account for the formation of other types of hydrothermal Au deposits.

Clay minerals are common in martian geological units and are globally widespread on Earth. Understanding the origin, formation, and alteration of clay minerals is crucial for unraveling past environmental conditions on Earth and Mars, in which the composition and crystallinity of clay minerals serve as important surrogate indicators for addressing these issues. Here, 621 soil and sediment samples from five chronosequences representing different climatic zones of China were investigated using visible to near-infrared reflectance (VNIR) in combination with X-ray diffraction (XRD) analysis. The crystallinity of clay minerals (i.e., illite crystallinity, illite chemistry index, kaolinite crystallinity) and clay mineral alteration index (CMAI) were analyzed with conventional methods and then predicted through a spectral modeling approach. Our results show that kaolinite with a pedogenic or sedimentary origin is characterized by a broad crystallinity range and a poorly ordered structure, especially when generated in an intense weathering environment. Predictive models were constructed with data-mining methods, including partial least-squares regression (PLSR), random forest (RF), and Cubist algorithms. The predictive performance of the crystallinity and CMAI proxies is robust, with an overall accuracy of 78% and a residual prediction deviation (RPD) of 2.57. We also found that the model’s accuracy in predicting clay-mineral-related proxies increased by 45% using random forest (RF) and Cubist compared to the PLSR models. We suggest that VNIR spectroscopy combined with RF and Cubist methods has the potential to be an alternative and broadly applicable tool for analyzing typical clay-mineral proxies, substituting for a series of common mineralogic analyses. Spectral modeling can reveal genetic and climatic information at both field and regional scales, which has profound implications for Mars missions and other space exploration programs.

The RRUFF online database (a project by Robert Downs, University of Arizona) catalogs the occurrence of point and space group symmetries of over 4800 of the nearly 6000 currently accepted mineral species. Of these, over 90% are monomorphic, while the remaining species have been recognized to be polymorphic. To avoid issues of reliability and inconsistency of characterization, the 4499 monomorphic minerals are the subject of this analysis. It has long been recognized that minerals are non-uniformly distributed among the space groups as well as their corresponding point groups and crystal systems. However, this non-uniformity is not non-systematic. A random distribution of minerals among the space groups would result in an average of about 20 species per group. In fact, the observed distribution of minerals is highly skewed. Analysis of the frequency distribution of minerals among the space groups reveals three distinct populations: those without currently known monomorphic species (52), those sparsely populated by minerals that exhibit an exponential distribution of species abundances (170), and those most populous space groups (8) that are differentiated from the others by an inflection in the slope of the species frequency distribution. Additionally, a series of relationships have been identified, and they collectively characterize crystallographic controls on and resultant distributions of mineral occurrence. First, there is a strong preference across all crystal systems for minerals to exhibit structures associated with the holohedral space groups relative to those pedial groups of the lowest symmetry. Second, mineral species exhibit a strong preference for the Laue class space groups over their paired Sohncke groups. Furthermore, it is recognized that the space groups that make up the 11 enantiomorphic pairs are either sparsely populated or devoid of known mineral species. Third, the centering types of the Bravais lattices and structures defined by the Wyckoff multiplicities of the various space groups are recognized to strongly influence the distribution of mineral species such that more structurally and symmetrically complex space groups (those with non-primitive lattice structures) tend to be represented by more minerals. Fourth, when considering the 73 arithmetic space group classes, inmost cases non-symmorphic space groups are more richly populated than their linked symmorphic space groups, and in those cases where both hemisymmorphic and asymmorphic space groups are present in the same arithmetic class, the asymmorphic space groups typically contain more species. Together, these observations and interpretations augment and advance previously achieved understandings of mineral frequency distributions among the point groups and imply four future lines of inquiry: extending consideration to polymorphic species as well as relating distributions among the space groups to terrestrial mineral species abundance, mineral chemistry, as well as the evolution of mineral chemistry and paragenesis.

Rutile is the most common TiO 2 mineral on Earth’s surface and transforms to CaCl 2 - and α-PbO 2 -type structures at elevated pressures in subducted basaltic crusts. In this study, we synthesized hydrous CaCl 2 - and α-PbO 2 -type TiO 2 crystals with various Al 3+ concentrations using a multi-anvil press. Al 3+ is incorporated into the CaCl 2 - and rutile-type phases mainly in the form of 3Ti 4+ = 4Al 3+ , while the coupled substitution of Ti 4+ =Al 3+ +H + is dominant in the α-PbO 2 -type structure, forming Ti 1 −x(AlH)x O2 solid solutions. Consequently, the water solubility in Al-bearing α-PbO 2 -type TiO 2 is at least one order of magnitude greater than those in rutile- and CaCl 2 -type TiO 2 phases, making TiO 2 a significant water carrier at the pressure-temperature ( P-T ) conditions in the mantle transition zone (410 to 660 km depth in deep Earth’s interior), when coexisting with Al 3+ and Fe 3+ . High- P and high- T Raman spectra were collected for these synthetic samples. The CaCl 2 - and α-PbO 2 -type phases irreversibly transform to a rutile-type structure at 950 K and ambient pressure. A reversible α-PbO 2 →baddeleyite phase transition in TiO 2 is detected at approximately P = 10 GPa and T = 300 K, and incorporating smaller amounts of Al 3+ cations increases the phase transition pressure. The lattice vibrational modes typically shift to lower frequencies at elevated temperature and higher frequencies with increasing pressure due to variations in Ti(Al)-O bond length with temperature or pressure. Fourier transform infrared (FTIR) spectroscopic measurements were conducted on the samples under high- T or high- P conditions. Both T - and P -dependences are negative for the OH stretching vibrations in these TiO 2 polymorphs, except that the OH bands in the α-PbO 2 -type samples exhibit a blueshift at elevated temperature. A negative linear correlation can be drawn between the measured OH stretching frequencies and the incorporated M 3+ O 6 quadratic elongation, which were computed based on first-principles calculations. The local octahedral distortion can provide useful insights for understanding the M 3+ and H + incorporation mechanisms in TiO 2 and SiO 2 structures.

This paper reports the first finding of oriented triphylite (LiFe 2+ PO 4 ) rods in fluorapatite. This observation was made in the contact zone between a metamorphosed rare-element pegmatite and its amphibolite wall rock at the Stankuvatske Li-ore deposit in the Ukrainian Shield. This contact zone consists of an exocontact, in which hornblende was altered to biotite, and an endocontact, which comprises four parallel mineral zones (aplitic, apatite, triphylite, and transitional). The needle-shaped triphylite inclusions were observed in greenish-blue apatite within the apatite zone. They are oriented parallel to structural nanochannels along the c -axis in apatite and were formed due to the infiltration of Li-rich, pegmatite-derived fluids into the apatite zone. Small amounts of pyrite, U-Th-rich and Fe-rich phases, as well as small mono-phase fluid inclusions of CO 2 , CO, and N 2 are associated with the oriented triphylite inclusions and record the character of fluid. The exo- and endocontacts were formed as a result of interaction between metasomatic fluids derived from the pegmatite (enriched in K, Na, Li, Rb, F, P, and Mn) with the host amphibolite. At the contact, the amphibolite was altered into the biotite zone during the first metasomatic stage; alteration of hornblende and plagioclase released Ca, Fe, and Mg toward the pegmatite, where these elements reacted with P, Li, and Mn to produce the apatite and triphylite zones during the second metasomatic stage. Acting like a geochemical barrier, the apatite zone in the endocontact inhibited the further escape of Li from the pegmatite, which now is a Li-ore deposit. The metasomatic processes observed in the Stankuvatske Li-ore deposit represent an example of apatite and triphylite formation at the contact between a pegmatite and a metabasite, which has metallogenetic implications.

The Paleozoic Aktogai Group in Kazakhstan ranks among the 30 largest porphyry Cu deposits globally. The Aktogai deposit is the largest one in the Aktogai Group and is characterized by intensive potassic alteration where the dominant orebody occurred. However, its mineralization processes still need to be clarified. Our investigation focused on the texture, trace elements, fluid inclusions, and in situ oxygen isotopes of the quartz from the ore-related tonalite porphyry and associated potassic alteration at Aktogai to trace the deposit’s mineralization processes. Ti-in-quartz thermobarometry, fluid inclusion microthermometry, and geological characteristics indicate that the ore-related magma at Aktogai originated from a shallow magma chamber at∼1.9 ± 0.5 kbar (∼7.2 ± 1.9 km) and intruded as the tonalite porphyry stock at ∼1.7–2.4 km. The potassic alteration and associated Cu mineralization comprise five types of veins (A1, A2, B1, B2, and C) and two types of altered rocks (biotite and K-feldspar). Among them, nine types of hydrothermal quartz were identified from early to late: (1) VQ A1 in A1 veins and RQ bt in biotite-altered rocks; (2)VQ A2 in A2 veins and RQ kfs in K-feldspar altered rocks; (3) VQ B1 in B1 veins and VQ B2E in B2 veins; and (4) quartz associated with Cu-Fe sulfides (VQ B2L , VQ BC , and VQ C ) in B and C veins. Titanium contents of the quartz decreased, while Al/Ti ratios increased from early to late. Fluid inclusion micro-thermometry and mineral thermometers reveal that VQ A 1, RQ bt , and hydrothermal biotite formed under high-temperature (∼470–560 °C) and ductile conditions. VQ A 2, RQ kfs , VQ B 1, and hydrothermal K-feldspar formed during the transition stage from ductile to brittle, with temperatures of ∼350–540 °C. The rapid decrease in pressure from lithostatic to hydrostatic pressure led to fluid boiling and minor involvement ofmeteoric water (∼11–14%) in the mineralizing fluid. Extensive recrystallization in VQ A1 to VQ B1 was associated with repeated cleavage and healing of the intrusion. With cooling, K-feldspar decomposition and hydrolysis increased. Fluid cooling and water-rock reactions resulted in the co-precipitation of Cu-Fe sulfides, white mica, chlorite, VQ BC , and VQ C at temperatures of ∼275–370 °C and brittle conditions. The Paleozoic Aktogai deposit exhibits formation depths and fluid evolution processes similar to Mesozoic and Cenozoic porphyry Cu deposits worldwide. The close association between Cu-Fe sulfides and later quartz formed under intermediate-temperature conditions at Aktogai implies that Cu-Fe sulfides are not precipitated under early high-temperature conditions in porphyry Cu deposits.

The coloration mechanism of Oregon sunstone is a classic and controversial topic in mineralogy because of the unique coexistence of anisotropic (green-red) and isotropic (red) color zones within single feldspar crystals. After nearly 50 years of research, no models proposed to date have satisfactorily accounted for all observed optical phenomena. Here, we present high-resolution transmission electron microscopy analyses of samples prepared by focused ion beam extraction along specific crystal directions. In both the anisotropic and the isotropic color zones, we observed Cu nanoparticles (NPs) included within plagioclase but with different geometries. In the isotropic (red) zone, NPs were randomly distributed nano-spheres or nano-ellipsoids (8.7–12 nm in diameter) with an aspect ratio of 1–1.3. In contrast, in dichroic (green/red) zones, NPs were directionally aligned nano-rods (8.5–21 nm along the long axis) with an aspect ratio of ∼2.5. We applied localized surface plasmon resonance (LSPR) theory to simulate absorption spectra and developed a model to explain the observed optical properties. LA-ICP-MS and polarized UV-Vis spectroscopy were also performed to confirm our conclusions. This study systematically reveals the existence and optical influence of variably shaped metal-NP inclusions in feldspar crystals. Furthermore, it demonstrates the necessity of including LSPR in the canon of mineral coloration mechanisms. Cu-NP-bearing labradorite has been shown to exhibit third-order nonlinear optical properties, and approaches that incorporate NP shapes and sizes will assist in designing NP-embedded optical materials with tailored optical properties.

Investigations into the crystal structure of gowerite are limited, and a comprehensive understanding of the H positions is lacking. Hence, in this study, we synthesized single crystals of gowerite under hydrothermal conditions and obtained reliable single-crystal X-ray diffraction data to determine the H positions, thereby facilitating elucidation of the structural characteristics and formation environment of gowerite. The crystal structure of synthetic gowerite, Ca[B 5 O 8 (OH)][B(OH) 3 ]·3H 2 O, is monoclinic with unit-cell parameters: a = 12.872(4), b = 16.326(4), c = 6.5634(18) Å, and β = 121.319(3)°, and volume V = 1178.3(6) Å 3 . The crystal symmetry corresponds to the space group P 2/ 1 a ; the unit cell contains four formula units ( Z = 4). The structure is refined via full-matrix least-squares on F 2 to a final R 1 index of 4.13% for 1730 unique observed [ F o ≥ 4σ( F o )] reflections, measured with Mo K α radiation. The locations of the H atoms are identified on the difference Fourier maps and refined considering constraints on O-H distances together with interatomic distances between the H atoms. The crystal structure is characterized by a curved, corrugated, two-dimensional sheet in the a-c plane, composed of double three-membered borate rings and Ca atoms coordinated to six O atoms from the double three-membered rings. The Ca atom is further coordinated to a H 2 O molecule, and an isolated B(OH) 3 triangle is oriented approximately perpendicular to the sheets. Hydrogen-bonding interactions solely govern the linkages between the sheets. Consequently, three H 2 O groups are accommodated in the spaces between the sheets. An important feature of gowerite is that within the triangle geometry, the B-O bond length between the B atom and the hydroxyl group cannot be clearly distinguished from that between the B and O atoms. Ab initio quantum chemical calculations reveal that the molecular orbitals are spatially well spread over the three-membered borate ring, indicating that the B atoms are connected to the O atoms through covalent bonding. During the secondary mineralization process, the structural units of the fundamental building blocks (FBBs) are released from parent borate minerals, such as colemanite, priceite, and hydroboracite, by mineral weathering and inherited by the FBBs in gowerite. In addressing gaps in the existing literature, this study provides further information on the crystal structure and structural characteristics of gowerite, shedding light on its possible formation environment and growth conditions.

Zhonghongite (IMA2023-046), ideally Cu 29 (As, Sb) 12 S 33 , is a new mineral discovered in the highsulfidation vein of the Jiama deposit (E 91°45 ʹ , N 29°42 ʹ ), southern Tibet, China. It forms complex inter-growths with watanabeite and tennantite-tetrahedrite, creating veined or massive aggregates ranging from millimeters to centimeters. Single crystals of zhonghongite are anhedral, and their sizes range from several micrometers to ∼100 μm. The mineral is gray with a black streak and metallic luster. It is brittle, with uneven fractures, and has a calculated density of 4.925 g/cm 3 . The average values of electron microprobe analyses (wt%) are: Cu 42.19, As 11.11, Sb 16.09, S 25.45, Hg 3.73, Mn 0.67, and Te 0.28. The empirical formula, based on 33 sulfur apfu, is (Cu 27.60 Hg 0.77 Mn 0.51 Fe 0.07 Ag 0.02 ) Σ28.97 (As 6.16 Sb 5.49 Te 0.09 ) Σ11.74 S 33 . In zhonghongite, the substitution of Sb for As is limited, with the atomic ratio of As/(As+Sb) ranging from 0.457 to 0.629. Hg, Mn, and Fe, withminor Cu, are divalent and serve for charge balance. Zhonghongite is orthorhombic, space group F 2 mm (42), a = 10.37741(5) Å, b = 14.69821(9) Å, c = 36.7645(2) Å, and V = 5607.66(5) Å 3 . The crystal structure was solved and refined by single-crystal X-ray diffraction with a final R 1 = 0.0235 for 27 028 (2467 unique) reflections. It is composed of individual AsS 3 tripyramids and clustered As 4 S 7 tripyramids, CuS 4 tetrahedra, and CuS 3 planar triangles, connected through corner S atoms in tetrahedral coordination and octahedral coordination with Cu and/or As. The structure is a derivative of a tetrahedrite-type structure. Zhonghongite was formed under high-temperature conditions and is classified as an intermediate-sulfidation state mineral.

Uramphite, (NH 4 )(UO 2 )(PO 4 )·3H 2 O, was found at Beshtau uranium deposit, Northern Caucasus, Russia, as the second world occurrence besides its type locality, Tura-Kavak uranium-coal deposit in Kyrgyzstan. In Beshtau, it occurs as yellow tabular crystals up to 0.3 mmgrouped in crusts on amatrix composed of albite, microcline, quartz, and chamosite in association with liebigite, meta-autunite, and plumbogummite. The empirical formula calculated on the basis of 6 O apfu and 3 H 2 O is [ (NH4)0.91 K0.08 ]Σ0.99${{\left[ {{\left( \text{N}{{\text{H}}_{4}} \right)}_{0.91}}~{{\text{K}}_{0.08}} \right]}_{\Sigma 0.99}}$ P0.99U1.016+O6⋅3H2O.${{\text{P}}_{0.99}}\text{U}_{1.01}^{6+}{{\text{O}}_{6}}\cdot 3{{\text{H}}_{2}}\text{O}.$According to single-crystal X-ray diffraction, uramphite is tetragonal, P 4/ nmm , with a = 6.9971(3), c = 8.9787(9) Å, V = 439.59(6) Å 3 , and Z = 2. The crystal structure was refined to R 1 = 3.28% for 255 unique observed reflections with | F o | ≥ 4σ F . A model for the distribution of H 2 O and NH4+$\text{NH}_{4}^{+}$molecules in the interlayer space based on the electron density distribution data is proposed. The mineral belongs to the meta-autunite group. The IR spectrum shows the splitting of the band of H-N-H bending vibrations into four components, which is explained here by the resonance splitting of a group of NH4+$\text{NH}_{4}^{+}$cations occurring around the fourfold axis at close distances from each other. Uramphite is related to uramarsite, (NH 4 )(UO 2 )(AsO 4 )·3H 2 O. The two minerals have similar crystal structures and IR spectra. However, 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 H 2 NH4+$\text{NH}_{4}^{+}$molecules in the interlayer space (planar and well organized in uramphite vs. disordered in uramarsite).

Mineral separates mounted in thin section help introduce mineralogy students to concepts of relief, color, pleochroism, and birefringence and serve as reference materials both for research and teaching. Here, a simple method is described to produce materials that can be sent to thin section manufacturers to construct sets of mineral mounts. The method is relatively inexpensive, requires only simple equipment and few skills, and allows mounting of multiple minerals (easily 10–20) in a single thin section. The key to the method is to create first a slurry of 500–1000 mg of each crushed mineral plus ∼300 mg (500 μL) of epoxy and use a microspoon spatula to spoon each slurry into a 4 cm long tube made from 6 mm (or ¼″) diameter, standard wall, glass tubing. After epoxy sets, the 4 cm long tubes can be bundled together and shipped to thin section makers, who can set the bundles in epoxy (ends down) and make 10 or more duplicate sections. Photomicrographs are presented for selected mineral reference slides produced by this method, along with detailed instructions on how to create them. These methods allow both randomly oriented mineral separates and oriented crystals to illustrate isotropic appearance in quartz and reverse pleochroism in tourmaline.