We investigated crystal structures and the mechanism of thermal expansion of weeksite and its synthetic analogues (K-, Rb-, Cs-) using a combination of geometrical-topological analysis and empirical methods (powder X-ray diffraction, infrared spectroscopy, scanning electron microscopy, single-crystal and powder X-ray variable-temperature diffraction). The weeksite sample studied herein was collected at the Anderson mine, Yavapai County, Arizona, USA. Its synthetic analogues were prepared using high-temperature approaches in sealed silica tubes. Natural weeksite is stable up to 860 ± 10°C; it dehydrates between 100–200°C. Its synthetic analogues with Rb and Cs are stable at least until 1000°C. Their thermal expansion is strongly anisotropic due to shear deformations of the crystal structure. The framework in the structure of weeksite can be regarded as a sequence of uranyl silicate layers linked by SiO4 tetrahedra. With increasing temperature, the angles at the Si–O–Si ‘hinges’ change, which causes the shear deformations. The differences in the thermal behaviour, including expansion anisotropy, are probably due to the nature (size) of the alkali cations occupying the cavities in the framework. The partial or complete replacement of Rb+ by Cs+ illustrates the zeolite-like nature of the uranyl silicate framework in weeksite. Therefore, its structure can be considered a possible candidate for the selective immobilization of 137Cs+ upon storing nuclear waste with little interference from the more abundant Na+ and K+.

The monazite supergroup minerals represent anhydrous phosphates, less frequently arsenates, silicates and chromates with general formula ABX4, monoclinic symmetry, space group P21/n (14), and Z = 4. The A site is occupied usually by REE (La3+ to Gd3+) and other large divalent to tetravalent cations (mainly Ca2+, Pb2+, Bi3+, Th4+ and U4+) in nine-fold coordination. The B-site is filled with cations in tetrahedral coordination (mainly P5+ and As5+, in specific cases also Si4+, Cr6+ and other cations). The anionic X site is usually occupied by O2– but may be replaced to a small extent by F– or an (OH)– anion. The supergroup is divided into one group: monazite (phosphates, arsenates, vanadates), and two unassigned members: huttonite (silicates) and crocoite (chromates, sulfates). Recently, eleven valid mineral species of the monazite supergroup were approved by the IMA-CNMNC: monazite-(La), monazite-(Ce), monazite-(Nd), monazite-(Sm), monazite-(Gd), cheralite, gasparite-(La), gasparite-(Ce), rooseveltite, huttonite, and crocoite. In addition, mineral analyses and synthesized compounds indicate the potential existence of several other new members of the monazite supergroup in natural environments.

The abundance and distribution of rare-earth elements (REE) within fish debris from the Japanese Exclusive Economic Zone around Minami-Torishima Island have been investigated to determine the host materials of REE in the REE-rich deep-sea mud. The study was performed using REE-extraction experiments, field emission electron probe microanalysis (FE-EPMA), transmission electron microscopy with an energy-dispersive X-ray spectrometer (TEM-EDX), laser-induced breakdown spectroscopy (LIBS), Fourier-transform infrared (FTIR) spectroscopy and X-ray absorption near edge structure (XANES) analysis.

The EPMA data indicate that the amount of REE in the apatite in the teeth is less than that in the bone debris. According to TEM-EDX analysis, yttrium (Y) is contained in the rod-like apatite crystals in the bone debris, but not in the long rod-like apatite crystals of the teeth. Analyses by LIBS and EPMA indicate that Y-rich bone debris is also rich in C. The FTIR spectroscopic analysis indicates the presence of carbonate groups within the Y-rich apatite structure. Moreover, the results of the XANES analysis and REE-extraction experiments indicate that Y occurs within the crystal structure of C-bearing apatite in the bone debris. These results suggest that the REE within C-bearing apatite in the fish debris from the Minami-Torishima REE-rich deep-sea mud substitute for Ca in apatite via an ionic exchange reaction, probably Ca2⁺ + P⁵⁺ ↔ REE3⁺ + C⁴⁺.

Terrestrial vascular plants affect Earth’s long-term geological processes, contributing to carbon cycling, chemical weathering and soil formation. Plants transport elements from the soil to their above-ground structures, accumulating a range of macroelements including Na, K, Mg, Ca, Si, S, P and Cl. Wildfire combustion concentrates these macroelements into inorganic ash. This ash is dominated by oxides, carbonates, halides, sulfates and phosphates of Na, K, Mg and Ca. This work describes K₂Ca₂(CO₃)₃, which occurs abundantly in the ash of the desert spoon (Dasylirion wheeleri), a plant native to the Sonoran Desert. Electron microprobe analysis, powder X-ray diffraction Rietveld refinement and Raman spectroscopy confirm that this phase matches synthetic rhombohedral (R3) K₂Ca₂(CO₃)₃. This phase forms during the smouldering combustion of D. wheeleri trunks, producing friable, decimetre-sized, porous, ash lumps that pseudomorphically preserve the plant’s fibrous structure. This ash occurs as glassy, sintered, porous aggregates, dominated by K₂Ca₂(CO₃)₃, with sylvite, calcite, fairchildite, arcanite and minor hydroxyapatite and periclase. Several double K–Ca carbonates form under surficial pressures and temperatures below ~800°C, including K₂Ca₂(CO₃)₃, and bütschliite (K₂Ca(CO₃)₂) and its dimorph, fairchildite. The occurrence of rhombohedral K₂Ca₂(CO₃)₃ and fairchildite are consistent with smouldering between 518 and 780°C. Upon exposure to water, K₂Ca₂(CO₃)₃ rapidly decomposes, leaving calcite. The occurrence of K₂Ca₂(CO₃)₃ as a major phase in the plant ash expands our understanding of Earth’s mineral diversity, provides new insights into the widespread geological process of wildfire ash formation and highlights the role that these fires play in forming mineral phases that are rare in other geological settings. Though K₂Ca₂(CO₃)₃ was first identified in Dasylirion wheeleri, this phase probably forms in other fire-adapted plant species. The occurrence of K₂Ca₂(CO₃)₃ in plant ash is an example of an inorganic phase that bridges the gap between biomineralisation and geological mineral formation.

Mineralogical crystallography has evolved from the geometric and observational studies of the eighteenth century to a dynamic, predictive science capable of probing matter at atomic and nano-scales. Contemporary advances, including ultrafast X-ray free-electron lasers, high-pressure diamond anvil cells, cryo- and environmental electron microscopy, and multimodal in situ techniques, now permit real-time observation of mineral transformations under extreme conditions. Coupled with computational modelling and predictive simulations, these methods are transforming crystallography into an integrative, interdisciplinary discipline with applications ranging from Earth and planetary sciences to materials engineering. This essay explores technological innovations and emerging frontiers of mineralogical crystallography, highlighting its enduring role in revealing the hidden architectures of matter and guiding the exploration of both natural and synthetic materials.

Earth’s lithospheric mantle is dominated (usually >90% vol.%) by a nominally volatile-free mineral paragenesis with peridotitic composition. The remaining lithologies are typically hydrous and/or carbonate-bearing assemblages (the latter mostly stable at P >2 GPa), representing the products of mantle metasomatism with, or without, involvement of subduction. Despite their importance, the modal compositions of these metasomes are poorly constrained, probably containing hydrous phases (amphibole and/or phlogopite), coupled with accessory minerals, such as apatite, ilmenite, rutile and/or carbonates. These assemblages are usually considered to be the source of unusual magmas, in particular ultrapotassic compositions, especially kamafugites (K2O-rich, commonly ultracalcic, basic/ultrabasic lithologies). To evaluate if partial melting of such metasomes could effectively produce kamafugites, we performed partial melting experiments at 2.7 and 5 GPa, and 1200°C to 1550°C on clinopyroxenites variably enriched in phlogopite, olivine and accessory phases (apatite, oxides, titanite), and on a clinopyroxene glimmerite (with apatite and magnetite).

At low degrees of melting, the glasses show extremely high TiO2 (<15 wt.%), CaO (<18 wt.%) and P2O5 (<7.4 wt.%), coupled with low SiO2 (>21.6 wt.%), as accessory minerals are the principal contributors in the melting reactions. Although there are no known natural counterparts for these low-degree melt compositions, they might play a key role in re-fertilisation events in the upper mantle. At increased degrees of partial melting (∼50 to ∼90%), the experimental melts approach the compositions of silica-poor, potassic/ultrapotassic and ultracalcic rocks. Indeed, experimental-produced glasses share several geochemical similarities with natural kamafugites, partially overlapping for most of the major oxides. Clinopyroxene- and phlogopite-rich lithologies, variably enriched in olivine and accessory phases (apatite, oxides, titanite) probably occur as veins pervading the lithospheric peridotitic matrix, and their partial melting, especially at high degrees, may be a plausible explanation for the genesis of SiO2-poor, K2O- and CaO-rich compositions.

The new mineral, zavyalovite, ideally Ag2TeS3, was found at the Boevskoe W-Be deposit, Chelyabinsk Oblast, Southern Urals, Russia. It occurs as very small anhedral grains (typically 5–15 μm, max. up to 30 μm across) or narrow veinlets (up to 100 × 5 μm) within galena or at the contact of galena and sphalerite. Zavyalovite is dark red, opaque with sub-metallic lustre, brittle tenacity and uneven fracture. No cleavage or parting was observed. The Vickers’ micro-indentation hardness (VHN, 10 g load) is 95 kg/mm2 (range 93–98, n = 4), corresponding to a Mohs hardness of 2.5. Dcalc. = 5.33 g/cm3. In reflected light of the ore microscope, zavyalovite is grey, very weakly bireflectant and non-pleochroic. Under crossed polarizers the new mineral exhibits strong anisotropy, in grey tones. Internal reflections are abundant, red in colour. The reflectance values for wavelengths recommended by the Commission on Ore Mineralogy of the International Mineralogical Association are (Rmin/Rmax, %): 32.2/31.8 (470 nm), 29.6/29.1 (546 nm), 28.4/27.5 (589 nm) and 27.3/26.5 (650 nm). The Raman spectrum shows bands corresponding to stretching and deformation vibrations in the TeS3 polyhedra. The chemical composition (wt.%, electron microprobe data, mean of eight spot analyses) is Ag 49.31, Te 29.04, S 21.75, total 100.10. The empirical formula calculated on the basis of six atoms per formula unit is Ag2.01Te1.00S2.99. Zavyalovite is monoclinic, space group Cc, with a = 6.8440(8), b = 11.515(1), c = 7.6529(7) Å, β = 114.47(1)°, V = 548.96(7) Å3 and Z = 4. The strongest lines of the powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 3.495 (73) (0 0 2), 3.242 (61) ($\bar 1$ 3 1), 3.017 (57) ($\bar 2$ 0 2), 2.749 (100) (1 3 1), 2.163 (22) (1 3 2), 2.131 (64) ($\bar 1$ 3 3), 1.941 (21) ($\bar 3$ 3 1). The crystal structure of zavyalovite is isotypic with synthetic Ag2TeS3. The new mineral honours Russian mineralogist, crystallographer and expert in sulfotellurides Dr Evgeniy N. Zavyalov (born 1944).

Cuprodongchuanite (IMA2021-065), Pb4CuZn2(PO4)2(PO4)2(OH)2, is a new mineral from Sanguozhuang Village, Yunnan Province, China. It occurs as striking apple green crust-like radial or spherical aggregates of microscopic blade-like crystals on hemimorphite. Cuprodongchuanite is brittle with an irregular fracture, a Mohs hardness of 2½–3, and perfect cleavage on {011}. The calculated density is 6.10 g/cm3. The empirical chemical formula is (Pb4.06Ca0.02)Σ4.08(Cu1.07Cd0.01)Σ1.08Zn2.03[(P0.74As0.20S0.01Si0.01)Σ0.96O4]2(PO4)2(OH)2 based on 18 O atoms per formula unit. Cuprodongchuanite is triclinic, space group P$\bar 1$(#2), with unit-cell parameters. a = 4.7405(3) Å, b = 8.5023(5) Å, c = 10.2897(6) Å, α = 97.206(5)°, β = 101.877(5)°, γ = 91.786(5)°, V = 401.95(4) Å3 and Z = 1. Cuprodongchuanite’s name combines the prefix ‘cupro’ (for copper) with the root ‘dongchuanite’. As a member of the dongchuanite group, cuprodongchuanite features a dongchuanite-type structure with the general formula A4VIBIVB2(X1O4)2(X2O4)2(OH)2. In addition to providing a detailed characterisation of cuprodongchuanite, this study delves deeper into exploring the Jahn-Teller effect of Cu2+ ions at the VIB site, an important factor in the mineral’s crystallography. Employing the Δoct parameter, the study quantitatively links the degree of octahedral distortion to the Cu-Zn ratio. This method provides a refined understanding of the dongchuanite-type structure and offers an example for assessing similar mineral compositions where cations exhibit closely related properties.

In the extreme thallium (Tl) environments, such as oxidation zones of Tl-bearing sulfide deposits including mining wastes and technosols, Tl is retained mostly through formation of secondary Tl minerals or Tl-adsorption onto micaceous phyllosilicates and illite-like clay minerals. To better understand Tl-retention processes and phase formation in such environments we have synthesized high-quality single crystals of three mineral-like Tl salts using hydrothermal methods. These are thallium(I) triiron(III) bis(sulfate) hexahydroxide doped by small amounts of K+ and Al3+, (Tl0.91K0.09)(Fe2.90Al0.10)(SO4)2(OH)6 (I), aluminium thallium bis(sulfate) dodecahydrate Tl+Al(SO4)2·12H2O (II) and ferric iron thallium bis(sulfate) Tl+Fe3+(SO4)2 (III). They were characterized through single-crystal X-ray diffraction (SCXRD), Fourier-transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX) and partly by transmission electron microscopy (TEM). The compounds I and III crystallise in trigonal centrosymmetric space groups: I in R$\overline 3 $m with a = 7.3330(4), c = 17.7118(6) Å and III in R$\overline 3 $ with a = 4.8375(2), c = 24.7905(9) Å, whereas II is cubic, space group Pa$\overline 3 $, with a = 12.2727(14) Å. I and II, are synthetic analogues of the minerals dorallcharite and lanmuchangite, respectively. Synthetic dorallcharite (I) is isostructural with minerals in the jarosite–alunite series, KFe3+3(SO4)2(OH)6–KAl3(SO4)2(OH)6, while synthetic lanmuchangite (II), nominally TlAl(SO4)2·12H2O, is a cubic thallium alum, a type of hydrated double sulfate salt isostructural with the β-alum, CsAl(SO4)2·12H2O. The crystal structure of III, TlFe3+(SO4)2, is like that of the mineral steklite, KAl(SO4)2. II and III chemically belong to the group of alums with different degrees of hydration. The O–H···O hydrogen bonds in I and II assemble water molecule H2O and hydroxide OH– ions into several various hydrogen bond networks. The structural connections to the related minerals and inorganic compounds of I–III have been discussed. Our findings provide new insights into the chemical and structural properties of dorallcharite and lanmuchangite, enhancing our understanding of their formation in Nature. The findings also suggest the potential natural occurrence of TlFe(SO4)2, offering valuable implications for the role of sulfates in the environmental cycling of Tl.

I present a new set of new rules for Crystal Chemistry that greatly increases our understanding of the factors affecting the stereochemistry of mineral and inorganic crystal structures.

The electric field in a crystal is a vector field; bond strengths from cations to anions are positive and bond strengths from anions to cations are negative. The incident bond strengths at all ion sites must equal the formal charges at those sites. Bond strengths along non-degenerate paths between symmetrically equivalent ions in the structure must sum to zero. This leads to rule 1: the a priori bond-strength rule: “A priori bond-strengths may be calculated for all bonds in a structure by constructing a bond-strength table that includes all bond-strengths as unknown variables. The corresponding charge-conservation matrix can be solved for all the unknown bond-strengths”. The resultant bond strengths depend only on the formal charges of the constituent ions and the bond topology of the structure. However, they correlate strongly with bond lengths.

Ion radii derived from experimental bond lengths do not represent the radii of ions in crystals as we cannot objectively divide bond lengths into the radii of the constituent ions. This leads to rule 2, the ion-radius rule: “Ratios of ion radii have no physical meaning whereas sums of ion radii can be used in crystal chemistry (e.g. correlating site occupancies with observed mean bond lengths).”

The characteristic Lewis acidity of a cation is defined as its characteristic bond strength, which is equal to its charge/characteristic-coordination-number. The characteristic Lewis basicity of an anion is defined as the characteristic strength of the bonds formed by the anion. This leads to rule 3, the bond-strength-matching rule: “Stable structures will form where the Lewis acidity of the cation closely matches the Lewis basicity of the anion.” Cation and anion coordination numbers adjust to optimize matching of Lewis acidities and Lewis basicities.

The hydrogen isotope composition of the mantle provides insight into the advection, melting and metasomatism of the mantle, and the Earth’s water cycle. Because of sampling challenges, most estimates for the hydrogen composition of the mantle have been derived from basaltic glasses rather than from direct samples of the mantle. We present the first direct measurement of D/H ratios in nominally anhydrous orthopyroxene and olivine inclusions hosted within diamonds. The diamond hosts were recovered from placer deposits in Guyana, South America. The diamond-hosted inclusions preserve a population with δD of –31 ± 59‰ (normalised to Vienna Standard Mean Ocean Water). This value is D-enriched relative to that expected for a homogeneous upper mantle and is similar to values measured for arc basalts. We introduce three explanations for the observed D-enrichment in the anhydrous silicate inclusions. The hydrogen isotopic composition of the mantle might simply be heterogeneous in space and/or time. The measured D-enrichment could instead preserve local heterogeneity produced by fluids genetically related to the crystallisation of the diamond hosts. Local and mantle-wide processes might also have operated in concert, and overprint each other. Diamond-hosted silicate inclusions preserve an underexplored record of Earth’s water cycle.

Kenomicrolite (IMA 2024-097), ideally □2Ta2[O4(OH)2]□, (where □ = vacancy) is a newly approved mineral species from the Volta Grande pegmatite, Nazareno, Minas Gerais, Brazil. It is the first member of the pyrochlore supergroup to exhibit dominant vacancies at both A and Y sites and a Ta-dominated B site, making it a tantalum oxyhydroxide. It occurs as an accessory mineral within a microlite group assemblage, probably of secondary origin via weathering-induced leaching and hydration of fluorcalciomicrolite. Kenomicrolite appears as pale orange, transparent, isotropic octahedral crystals up to 200 μm in size, with a calculated density of 5.599 g·cm⁻3 and calculated refractive index of 1.880. Its empirical formula is A(□1.61Ba0.29Ce0.03U0.03Pb0.02Mn0.01Sr0.01)Σ2.00B(Ta1.74Nb0.11Sn0.08Si0.05Al0.01Ti0.01)Σ2.00 X[O4.65(OH)1.35]Σ6.00Y[□0.57(H2O)0.35F0.07K0.01]Σ1.00. The structure has been determined by single-crystal X-ray diffraction in the $Fd\bar 3m$ space group type, with a = 10.5911(6) Å. Spectroscopic analyses confirmed the presence of structural water primarily at the Y site. Ion-exchange experiments in Tl+-rich solutions showed minimal incorporation (∼0.19 Tl+ pfu), highlighting limited ion-exchange capacity due to vacancy-dominated tunnel sites. The structural stability and low hydration make kenomicrolite an important end-member for understanding vacancy-rich pyrochlore systems and their constraints on ion incorporation mechanisms.

The new mineral argentopearceite (IMA2020-049) was found at the mine dump of the abandoned Lehnschafter mine, Mikulov–Hrob district (holotype), and later at museum samples (cotypes) from the Moldava fluorite deposit, both in the Krušné hory Mountains, Czech Republic. Argentopearceite is associated with proustite in quartz gangue (Mikulov) or acanthite and proustite in fluorite gangue (Moldava). The new mineral occurs as tabular (pseudo)hexagonal crystals up to 0.8 mm (Mikulov) and 3 mm (Moldava), and as groups and aggregates up to 1 cm. Argentopearceite from Mikulov is steel grey to black. Mohs hardness is ca. 3; the calculated density is 6.29 g.cm–3. In reflected light, argentopearceite is grey with a greenish shade. Bireflectance was not observed and pleochroism is very weak. Anisotropy under crossed polars is moderate with weak greenish and green–blue tints. Internal reflections were not observed. Reflectance values of argentopearceite in air (Rmin/Rmax, %) are: 27.3/30.0 at 470 nm, 26.6/29.3 at 546 nm, 26.2/28.8 at 589 nm, and 25.9/28.1 at 650 nm). The empirical formula for argentopearceite, based on electron-microprobe analyses (n = 15), is (Ag15.95Cd0.02)Σ15.97(As1.82Sb0.11)Σ1.93(S11.03Cl0.05Te0.01)Σ11.09. The ideal formula is Ag16As2S11, which requires (in wt.%) Ag 77.45, As 6.72 and S 15.83, total of 100.00. Argentopearceite is trigonal, P321, a = 14.8583(5), c = 12.3038(15) Å, with V = 2352.38(15) Å3 and Z = 4. Its crystal structure was refined by single-crystal X-ray diffraction data to a final R1 = 0.0773 on the basis of 6594 unique reflections with Fo > 3σ(F) and 242 refined parameters. The structure of argentopearceite mostly conforms to the general architecture of the As-dominant members of the pearceite–polybasite family of minerals.

Anomalously high amounts of orthopyroxene are an unexpected feature of some depleted peridotite xenoliths from the cratonic lithosphere. This investigation presents new petrographic, geochemical and thermodynamic modelling data for silica-rich spinel harzburgites and one garnet–spinel harzburgite from the Kaapvaal Craton, South Africa, to constrain the pressure–temperature (P–T) conditions of orthopyroxene formation. At the time of sampling by the host kimberlite, the garnet–spinel harzburgite resided on the geotherm at 25 kbar, 765°C, wheras the compositionally similar garnet-free samples probably equilibrated at broadly comparable P–T conditions. The samples are subdivided into ‘bronzite type’ peridotites characterised by orthopyroxene with micrometre scale exsolutions of spinel ± clinopyroxene, and ‘normal type’ peridotites in which orthopyroxene does not contain visible exsolved phases. The presence of these exsolved phases indicates unmixing from a more Al-Cr-(Ca)-rich precursor orthopyroxene i.e. an original orthopyroxene that precipitated from, and was, in equilibrium with the Si-enriching agent at high temperature, before cooling and undergoing sub-solidus re-equilibration to form the exsolved orthopyroxene we observe now. Major and trace element compositions, geochemical interpretation and thermodynamic modelling of the samples show that the precursor orthopyroxene coexisted with melt at high pressure and temperature (~40–50 kbar, 1600–1700°C) within the garnet stability field. We consider these to be the conditions of orthopyroxene formation, and thus silica enrichment. These conditions, together with the refractory composition of the host peridotite (olivine forsterite contents > 92) suggest that silica enrichment is a secondary process potentially resulting from interaction with komatiitic melts. Our observations demonstrate that orthopyroxene enrichment in spinel-facies peridotites is not limited to low-pressure processes but can also occur via high-pressure melt–rock interaction, offering new insights into the thermal and chemical evolution of the sub-cratonic lithospheric mantle.

Single-crystal synchrotron X-ray diffraction data were collected up to 10 GPa at room temperature on a natural omphacite with composition close to Jd43Di57, at the Xpress beamline at Elettra Synchrotron, using a diamond anvil cell. A second-order Birch-Murnaghan equation of state (EoS) fit to the unit-cell volumes determined at 20 pressure points yielded V0 = 422.85(15) Å3, and K0 = 121.3(1.2) GPa. These elastic parameters are consistent with the general trend of the diopside–jadeite join. The structural evolution with pressure was determined from both ab initio simulations and structure refinements to the X-ray intensity data. The consistency between experimental findings and local geometrical distortions identified through ab initio calculations is discussed. A distortion variation at the M1 polyhedron occurs at ∼3 GPa, which correlates with the TILT angle of the T2 tetrahedron which stabilises at a similar pressure, coinciding with a decrease in the rate of M1 deformation under pressure.

These results revealing the structural evolution with pressure correlate with changes observed previously in some Raman shifts in the same pressure range in the same material.

New crystallographic data are reported for pseudojohannite, Cu3(OH)2[(UO2)4O4(SO4)2](H2O)12, from the type locality Jáchymov, Czech Republic. The structure refinement is based on a dataset collected with high redundancy (8.62) using a brilliant X-ray microfocus source, which provided sufficient quality to localize hydrogen atoms from difference-Fourier maps. The pseudojohannite crystal studied is triclinic at 100 K, with the space group P$\overline 1 $, with a = 8.6697(4), b = 8.8712(5), c = 9.9825(6) Å, α = 71.775(6)°, β = 70.663(5)°, γ = 76.011(5)°, with V = 679.88(7) Å3 and Z = 1. The final refinement converged to R1 = 0.0198 for 6029 unique reflections with I > 3σ(I) and wR2 = 0.0699 for all 6924 reflections. The bond-valence analysis for the structure and the determined positions of H atoms provided complete information on the nature of bonding between the [(UO2)4O4(SO4)2] structural units and the interlayer complex in pseudojohannite. In total, there are eight transformer H2O groups, four non-transformer H2O (two of which are not directly linked to any metal cation sites), and two OH– groups. The structure formula of pseudojohannite can be written as Cu3(H2[3]O)8(H2[4]O)2(OH)2[(UO2)4O4(SO4)2](H2[4]O)2 (Z = 1). Pseudojohannite represents a well-ordered triclinic zippeite-type structure.

Arsenoveszelyite, Cu2Zn(AsO4)(OH)3·2H2O, is a new supergene mineral from the Dongchuan copper ore field, Yunnan Province, China. It is the arsenic analogue of veszelyite and has been approved by the IMA CNMNC (IMA2021-076a). Arsenoveszelyite occurs as radiating aggregates or as individual lamellar crystals. Its colour ranges from cyan to emerald green, and it is closely associated with azurite and hemimorphite in the intensely weathered zones of the locality. Arsenoveszelyite has a Mohs hardness of 3–4 and a mean Vickers hardness of 265.0 kg/mm2. It shows good cleavage on {001} and {110}, is brittle with irregular fracture, and has a calculated density of 3.61 g/cm3. Optically, it is biaxial (+) with refractive indices nα = 1.655(10), nβ = 1.665(5), and nγ = 1.690(10); the optical orientation is defined as Y = b, and the measured 2V angle is 40°. The mineral is monoclinic, space group P21/c, with unit-cell parameters a = 7.5852(4), b = 10.3877(5), c = 9.8714(5) Å, β = 102.984(5)°, and V = 757.91(7) Å3. The crystal structure of arsenoveszelyite is characterized by the regular alternation of octahedral and tetrahedral sheets parallel to the (001) plane. The octahedral sheets comprise two distinct types of Cu-centred octahedra, while the tetrahedral sheets are formed by a combination of Zn- and As-centred tetrahedra. The empirical formula of arsenoveszelyite is (Cu1.69Zn0.30)Σ1.99Zn[(As0.81P0.20)Σ1.01O4](OH)3.03·2H2O. Arsenoveszelyite is the fourth new mineral identified in the Dongchuan copper ore field with arsenic as the dominant occupant of a crystallographic site, providing new insights into the mechanisms by which arsenic is immobilized in crystal structures during weathering in this area.

Twenty extra-framework S- and C-bearing species including anions (SO42–, SO32–, S2–, S52–, HS–, CO32–, C2O42– and HCO4–), radical anions (S2•–, S3•–, cis- and trans-S4•– and SO4•–) and neutral molecules (CO2, COS, H2S, cis- and trans-S4 and S6) have been identified in natural tectosilicates (members of the sodalite, cancrinite and scapolite groups) using a novel multimethodic approach based on several spectroscopic methods, single-crystal and powder X-ray diffraction, and electron microprobe and wet chemical analyses. Various polysulfide groups were detected in lazurite, haüyne, vladimirivanovite, sapozhnikovite, slyudyankaite, kyanoxalite, balliranoite, marinellite, tounkite, bystrite, sulfhydrylbystrite and meionite. Experimental data on mutual conversions of S-bearing species and structure modulations of these minerals under different temperatures, reducing and oxidizing environment as well as radiation-induced conversions provide a key for their use as markers of the crystallization or transformation conditions in Nature and during synthesis and modification.