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, Diana O. Nekrasova, Dmitry O. Charkin, Anatoly N. Zaitsev, Artem S. Borisov, Marie Colmont, Olivier Mentré, Darya V. Spiridonova
Published: 29 September 2021
Mineralogical Magazine pp 1-29; https://doi.org/10.1180/mgm.2021.73

, Harald Müller, Matteo Leoni
Published: 17 September 2021
Mineralogical Magazine pp 1-8; https://doi.org/10.1180/mgm.2021.66

Abstract:
The synthesis and structure of the title compound, 1, is presented, refined using Rietveld against powder X-ray diffraction data. 1 crystallises dominantly in a pseudotetragonal C-centred orthorhombic lattice with dimensions a = 6.6791(6) Å, b = 15.5006(6) Å, c = 6.6811(6) Å and V = 691.70(10) Å3. The structural model proposed here refined by Rietveld is Sr0.928(8)Cu4(OH)8Cl2⋅3.60(21)H2O in space group Cmcm (63), with Z = 2. The chemistry and diffraction pattern of 1 are similar to that for the known Ca analogue, calumetite. The copper sites are arranged with square planar coordination at ¼ and ¾ height and are bonded to four (protonated) oxygens at an average of 1.966 Å (effective coordination of 3.82 Å). The more distant Cl sites (at Cu−Cl = 3.190(6) Å) complete the heavily Jahn–Teller distorted Cu[(OH)4,Cl2] polyhedra. The ½-occupied Sr sites are 8 coordinated to four protonated oxygens shared with the Cu-layer (at 2 × 2.438(8) Å, 2 × 2.566(15) Å) and by 4 bonds to the proposed water sites (Sr−Ow = 2.760(9) Å). The structure of 1 is predisposed towards defects, based on a notional tetragonal, P4/nmm, substructure with a sub ≈ a 1, csub = b ½ dimensions. Average diffraction models have been further elaborated in order to resolve additional peaks (and peak-shapes) using DIFFaX+.
, Nikita V. Chukanov, Erik Jonsson, Igor V. Pekov, Dmitry I. Belakovskiy, Marina F. Vigasina, Natalia V. Zubkova, Konstantin V. Van, Sergey N. Britvin
Published: 2 September 2021
Mineralogical Magazine pp 1-10; https://doi.org/10.1180/mgm.2021.70

Abstract:
The new wermlandite-group mineral erssonite, ideally CaMg7Fe3+ 2(OH)18(SO4)2⋅12H2O (or [Mg7Fe3+ 2(OH)18][Ca(SO4)2]⋅12H2O), was discovered in a late-stage, low-temperature assemblage in cavities of a magnetite-bearing dolomitic rock from the Långban deposit, Värmland county, Bergslagen ore province, Sweden. The associated minerals are dolomite, calcite, members of the magnetite–magnesioferrite solid-solution series, phlogopite, chrysotile, pyroaurite and norbergite. Erssonite has a vitreous lustre and forms colourless, platy hexagonal crystals flattened on [0001], up to 0.5 mm across and up to 10 μm thick, occurring mainly as aggregates in cavities of dolomitic rock. Erssonite is malleable; separate crystals are flexible and non-elastic, with a perfect, mica-like cleavage on {0001}. The calculated density is equal to 2.02 g⋅cm–3. Raman spectroscopy shows the presence of typical bands for S–O bonds attributed to intercalated SO4 2– anions and structural OH– anions together with the absence of C–O bonds, attributed to carbonate anions. The chemical composition is (wt.%, electron microprobe, H2O content is calculated from structure data): MgO 28.67, CaO 2.76, Al2O3 0.23, Cr2O3 0.23, Fe2O3 16.00, SiO2 0.48, SO3 14.80, H2O 35.58, total 98.75. The empirical formula based on 38 O atoms is H41.48Ca0.52Mg7.47Fe3+ 2.11Al0.05Cr0.03S1.94Si0.08O38. The ideal formula is CaMg7Fe3+ 2(OH)18(SO4)2⋅12H2O or {Mg7Fe3+ 2(OH)18}{[Ca(H2O)6](SO4)2(H2O)6}. The crystal structure was determined using single-crystal X-ray diffraction data and refined to R = 0.093. Erssonite is trigonal, P $\bar{3}$ c1, with a = 9.3550(6), c = 22.5462(14) Å, V = 1708.8(2) Å3 and Z = 2. The strongest lines of the powder X-ray diffraction pattern [d, Å (I, %)(hkl)] are: 11.22 (90)(002), 5.63 (64)(004), 4.670 (100)(110, 104, 014), 2.626 (64)(032, 302), 2.435 (66)(034, 304) and 1.951 (45)(038, 308). The mineral is named in honour of the Swedish amateur mineralogist Dr. Anders Ersson (b. 1971).
, Daniela Pinto, Donatella Mitolo, Uwe Kolitsch
Published: 1 September 2021
Mineralogical Magazine pp 1-8; https://doi.org/10.1180/mgm.2021.69

Abstract:
Thermessaite-(NH4), ideally (NH4)2AlF3(SO4), is a new mineral found as a medium- to high-temperature (~250–300°C) fumarole encrustation at the rim of La Fossa crater, Vulcano, Aeolian Islands, Italy. The mineral deposited as aggregates of minute (<0.2 mm) sharp prismatic crystals on the surface of a pyroclastic breccia in association with thermessaite, sulfur, arcanite, mascagnite, and intermediate members of the arcanite–mascagnite series. The new mineral is colourless to white, transparent, non-fluorescent, has a vitreous lustre, and a white streak. The calculated density is 2.185 g/cm3. Thermessaite-(NH4) is orthorhombic, space group Pbcn, with a = 11.3005(3) Å, b = 8.6125(3) Å, c = 6.8501(2) Å, V = 666.69(4) Å3 and Z = 4. The eight strongest reflections in the powder X-ray diffraction data [d in Å (I)(hkl)] are: 5.65 (100)(200), 4.84 (89)(111), 6.85 (74)(110), 3.06 (56)(112), 3.06 (53)(221), 3.08 (47)(311), 2.68 (28)(022) and 2.78 (26)(130). The average chemical composition, determined by quantitative SEM-EDS (N by difference), is (wt.%): K2O 3.38, Al2O3 25.35, SO3 36.58, F 26.12, (NH4)2O 22.47, O = F –11.00, total 102.90. The empirical chemical formula, calculated on the basis of 7 anions per formula unit, is [(NH4)1.85K0.15]Σ2.00Al1.06F2.94S0.98O3.06. The crystal structure, determined from single-crystal X-ray diffraction data [R(F) = 0.0367], is characterised by corner-sharing AlF4O2 octahedra which form [001] octahedral chains by sharing two trans fluoride atoms [Al–F2 = 1.8394(6) Å]. Non-bridging Al–F1 distances are shorter [1.756(1) Å]. The two trans oxygen atoms [Al–O = 1.920(2) Å] are from SO4 tetrahedra. NH4 + ions occur in layers parallel to (100) which alternate regularly with (100) layers containing ribbons of corner-sharing AlF4O2 octahedra and associated SO4 groups. The NH4 + ions are surrounded by five oxygen atoms and by four fluorine atoms. The mineral is named as the (NH4)-analogue of thermessaite, K2AlF3(SO4), and corresponds to an anthropogenic phase found in the burning Anna I coal dump of the Anna mine, Aachen, Germany. Both mineral and mineral name have been approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification (IMA2011-077).
Published: 19 August 2021
Mineralogical Magazine pp 1-24; https://doi.org/10.1180/mgm.2021.65

Abstract:
Amphibole and biotite were the principal mafic minerals precipitated during the magmatic and post-magmatic (including hydrothermal) crystallisation stages of coeval metaluminous to slightly peraluminous syenogranites and peralkaline alkali-feldspar granites of the Mandira Granite Massif, in the post-collisional A-type Graciosa Province, S-SE Brazil. Magmatic calcic (ferro-ferri-hornblende and hastingsite) amphiboles occur in the metaluminous syenogranites, whereas calcic (ferro-edenite), sodic–calcic (ferro-ferri-winchite) and sodic (arfvedsonite and riebeckite) amphiboles occur in peralkaline alkali-feldspar granites. Rare earth element (REE) contents decrease from hornblende to winchite and riebeckite, and the partition coefficients indicate increasing compatibility from light rare earth elements (LREE) to heavy rare earth elements (HREE), with a marked preference for the HREE over the LREE in the sodic–calcic and, particularly, the sodic amphiboles. Post-magmatic calcic- (ferro-actinolite) and sodic- (riebeckite) amphiboles are also present in the peralkaline granites. Magmatic biotite (annite) is dominant in syenogranites, whereas post-magmatic annite and late-to post-magmatic annite evolving to siderophyllite occurs in the peralkaline granites. Typical hydrothermal phyllosilicates are chlorite (chamosite) in syenogranites and related greisens, and ferri-stilpnomelane which is present in both peralkaline granites and metaluminous syenogranites. Lithostatic pressure estimates suggest that the main granites were emplaced under pressures of ~93–230 MPa, with close-to-liquidus temperatures varying from ~830°C for syenogranites to ~900°C for the peralkaline granites. The original magmas crystallised mainly under relatively reduced (buffered at ~ –1 ≤ QFM ≤ 0), and more oxidising (somewhat above QFM) environments, respectively. Chlorite, replacing biotite in syenogranites and as the main mineral in the related greisens, permits the temperature of the main hydrothermal event to have taken place between 250 and 272°C. Estimated log (f HF/f HCl) values from biotite compositions vary from ~ –2 to –1 (syenogranites) and ~ –3.5 to –2 (peralkaline granites) and indicate F preference over Cl in the hydrothermal fluid phase.
D. Küster, , Emanetoullah Limam, Omar Jatlaoui, Oumar Ba, Abdellahi Maham Zein Mohamed, M. Pohlmann-Lortz, M. Ranneberg, K. Ufer
Published: 11 August 2021
Clay Minerals pp 1-14; https://doi.org/10.1180/clm.2021.26

Abstract:
Non-metallic raw materials are largely unexplored in many African countries. In an attempt to reduce this knowledge gap, kaolin occurrences in three promising regions of southern Mauritania were examined. The aim of the paper is to describe the occurrences and characterize the material in terms of mineralogy and potential technical use in the ceramics industry. The kaolins are geologically associated with various sedimentary rock units in either the Coastal Basin (Kaédi), the Mauritanide Belt (Hassi Abyad) or the Taoudeni Basin (Néma). Geochemical data show Al2O3 contents of between 9% and 38% (corresponding to 23–96% kaolinite). Samples from the Hassi Abyad and Kaédi regions have greater kaolinite contents on average and were further investigated mineralogically. The kaolin from the Néma region contained less kaolinite (<50 mass%). The region is also less accessible and hence is not considered further in this study. X-ray diffraction, X-ray fluorescence and infrared spectroscopy confirmed the geochemically calculated kaolinite contents of the kaolins and identified quartz, anatase and goethite as the remaining major mineral constituents. The degree of structural disorder of the kaolinites (determined by infrared spectroscopy) is generally greater in the Kaédi occurrences than at Hassi Abyad. Ceramic tests proved that all of these kaolin raw materials might be used for the production of ceramics, and some may even be used for fine ceramics. From an economic point of view, the Hassi Abyad deposit is interesting in terms of its quality and reserves, aspects that will be addressed in detail in a follow-up study.
, Natalia V. Zubkova, Igor V. Pekov, Nikita V. Chukanov, Radek Škoda, Atali A. Agakhanov, Dmitriy I. Belakovskiy, Sergey N. Britvin, Dmitry Yu. Pushcharovsky
Published: 3 August 2021
Mineralogical Magazine pp 1-32; https://doi.org/10.1180/mgm.2021.64

Abstract:
Three new isostructural minerals, alexkuznetsovite-(La), ideally La2Mn(CO3)(Si2O7), alexkuznetsovite-(Ce) Ce2Mn(CO3)(Si2O7) and biraite-(La) La2Fe2+(CO3)(Si2O7), were discovered in polymineralic nodules from the Mochalin Log REE deposit, South Urals, Russia. The new minerals form anhedral grains up to 0.3 mm × 0.4 mm [alexkuznetsovite-(La)], 0.5 mm × 0.9 mm [alexkuznetsovite-(Ce)] and 0.2 mm × 1.2 mm [biraite-(La)] embedded in granular aggregates consisting of different REE minerals [allanite-(Ce)/-(La), bastnäsite-(Ce)/-(La), fluorbritholite-(Ce), perbøeite-(Ce)/-(La), percleveite-(Ce)/-(La) and törnebohmite-(Ce)/-(La)]. All three new species are brown to dark brown, translucent in thin fragments, with white streak, vitreous lustre and Mohs’ hardness of ~5. Dcalc = 4.713 [alexkuznetsovite-(La)], 4.687 [alexkuznetsovite-(Ce)] and 4.682 [biraite-La)] g⋅cm–3. Their empirical formulae, calculated on the basis of 2 Si and 10 O apfu, are: alexkuznetsovite-(La): (La0.98Ce0.89Nd0.10Pr0.05)Σ2.02Mn2+0.50Fe2+0.29Ca0.12Mg0.03(CO3)0.94(HCO3)0.06 (Si2O7); alexkuznetsovite-(Ce): (Ce0.96La0.78Nd0.16Pr0.07)Σ1.97Th0.01Mn2+0.50Fe2+0.33Ca0.14Mg0.02(CO3)0.93(HCO3)0.07(Si2O7); and biraite-(La): (La0.95Ce0.87Nd0.08Pr0.04)Σ1.94Th0.01Ca0.12Fe2+0.44Mn2+0.38Mg0.07(CO3)0.88(HCO3)0.12(Si2O7). The new minerals are monoclinic, P21/c and Z = 4. The unit-cell parameters of alexkuznetsovite-(La)/alexkuznetsovite-(Ce)/biraite-(La) are: a = 6.5642(3)/6.5764(4)/6.5660(10), b = 6.7689(3)/6.7685(4)/6.7666(11), c = 18.7213(10)/18.7493(15)/18.698(3) Å, β = 108.684(6)/108.672(8)/108.952(16)° and V = 788.00(7)/790.66(10)/785.7(2) Å3. The crystal structures are solved from single-crystal X-ray diffraction data; R = 0.0628 [alexkuznetsovite-(La)], 0.0589 [alexkuznetsovite-(Ce)] and 0.1193 [biraite-(La)]. A new biraite group is defined; it includes isostructural biraite-(Ce) and the three new minerals described herein. The rootname alexkuznetsovite is given in honour of the Russian mineral collector Alexey M. Kuznetsov (born 1962) who provided samples in which all three new minerals were found. The Levinson's suffix-modifier -(La) or -(Ce) indicates the predominance of La or Ce among REE in the mineral. Biraite-(La) is named as an analogue of biraite-(Ce) with La prevailing among REE.
, Gerhard Möhn, Fabrice Dal Bo, Natalia V. Zubkova, Dmitry A. Varlamov, Igor V. Pekov, Laurent Jouffret, Jean-Marc Henot, Pascal Chollet, Yannick Vessely, et al.
Published: 2 August 2021
Mineralogical Magazine pp 1-27; https://doi.org/10.1180/mgm.2021.63

, Jiří Sejkora, Thomas Raber, Philippe Roth, Yves Moëlo, Zdenĕk Dolníček, Marco Pasero
Published: 19 July 2021
Mineralogical Magazine pp 1-8; https://doi.org/10.1180/mgm.2021.59

Abstract:
Tennantite-(Hg), Cu6(Cu4Hg2)As4S13, was approved as a new mineral species (IMA2020-063) from the Lengenbach quarry, Imfeld, Binn Valley, Canton Valais, Switzerland. It was identified as an aggregate of black metallic tetrahedral crystals, less than 0.1 mm in size, intimately associated with sinnerite, and grown on realgar. In reflected light, tennantite-(Hg) is isotropic, grey in colour, with creamy tints. Minimum and maximum reflectance data for COM wavelengths in air are [λ (nm): R (%)]: 470: 29.1; 546: 29.1; 589: 28.5; 650: 27.7. Electron microprobe analysis gave (in wt.% – average of 7 spot analyses): Cu 32.57(42), Ag 6.38(19), Tl 0.29(14), Zn 0.04(5), Hg 17.94(2.27), Pb 0.70(51), As 17.83(61), Sb 0.34(8), S 24.10(41), total 100.19(1.04). The empirical formula of the sample studied, recalculated on the basis of ΣMe = 16 atoms per formula unit, is (Cu4.69Ag1.04Tl0.03)Σ5.76(Cu4.35Hg1.58Pb0.06Zn0.01)Σ6.00(As4.20Sb0.05)Σ4.25S13.26. Tennantite-(Hg) is cubic, I $\overline 4$ 3m, with a = 10.455(7) Å, V = 1143(2) Å3 and Z = 2. The crystal structure of tennantite-(Hg) has been refined by single-crystal X-ray diffraction data to a final R 1 = 0.0897 on the basis of 214 unique reflections with F o > 4σ(F o) and 22 refined parameters. Tennantite-(Hg) is isotypic with other members of the tetrahedrite group. Mercury is hosted at the tetrahedrally coordinated M(1) site, in accord with the relatively long M(1)–S(1) distance (2.389 Å), similar to that observed in tetrahedrite-(Hg). Minor Ag is located at the triangularly-coordinated and split M(2) site. Other occurrences of tennantite-(Hg) are briefly reviewed and the Lengenbach finding is described within the framework of previous knowledge about the Hg mineralogy at this locality.
Štěpán Chládek, Pavel Uher, Milan Novák, Peter Bačík, Tomáš Opletal
Published: 14 July 2021
Mineralogical Magazine pp 1-19; https://doi.org/10.1180/mgm.2021.58

Abstract:
Microlite-group minerals occur as common replacement products after primary and secondary columbite-group minerals (CGM) in albitised blocky K-feldspar and in coarse-grained, muscovite-rich units of the Schinderhübel I, Scheibengraben and Bienergraben beryl–columbite pegmatites in the Maršíkov District (Silesian Unit, Bohemian Massif, Czech Republic). Textural and compositional variations of microlite-group minerals were examined using electron probe micro-analyses and microRaman spectroscopy (μRS). A complex post-magmatic evolution of the pegmatites and the following microlite populations (Mic) and related processes were found: (1) precipitation of U, Na-rich and F-poor Mic I on cracks in CGM; (2) alteration of Mic I to U-rich together with Na- and F-poor Mic II; and (3) partial replacement of Mic I and II by Mic III with a distinct Na, U and Ti loss and Ca and F gain. Stage (2) includes an extensive leaching of Na, without U loss. The final stage (3) produced euhedral-to-subhedral oscillatory zoned Ca and F enriched Mic III with distinctly different composition to the previous F-poor and A-site vacant Mic II. Aggregates of fersmite are associated commonly with Mic III. Distal Mic IIId occurs locally on cracks in K-feldspar or quartz, with compositions analogous to Mic III. Compositional variations and textural features of microlite-group minerals during dissolution–reprecipitation processes serve as sensitive tracers of post-magmatic evolution in granitic pegmatites recording complex interactions between magmatic pegmatite units and externally derived, hydrothermal metamorphic fluids.
Bo Wu, Weijuan Zhao
Published: 13 July 2021
Clay Minerals pp 1-9; https://doi.org/10.1180/clm.2021.24

Abstract:
The Qingliang Temple kiln located in Baofeng County, Henan Province, China, is the discovery site of Ru Kuan porcelain, which is one of the five famous porcelain types of the Song dynasty in China. The ‘Ru-type ware’ and unglazed firing bodies were unearthed from the Qingliang Temple kiln in 2014, and the excavation site was very close to the central firing area of Ru Kuan porcelain. In this paper, the chemical composition, firing temperature and phase structure of the Ru-type ware and unglazed firing bodies from the Qingliang Temple kiln were analysed systematically using energy-dispersive X-ray fluorescence spectrometry, high-temperature thermal expansion and X-ray diffraction. The raw-material sources of the Ru-type ware bodies with various glaze colours are consistent but differ significantly from those of the unglazed firing bodies. The firing temperatures of the Ru-type ware and unglazed firing bodies are 1150–1200°C and 950°C, respectively, which are considered underfired. Mullite, α-quartz, β-cristobalite and α-Fe2O3 are the main constituents of the Ru-type ware bodies, whereas α-quartz and anatase were identified in the unglazed firing bodies. The Ru-type ware is related to the Ru Kuan ware in terms of firing techniques and official use.
Frank C. Hawthorne, Stuart J. Mills, Frédéric Hatert, Mike S. Rumsey
Published: 12 July 2021
Mineralogical Magazine pp 1-1; https://doi.org/10.1180/mgm.2021.54

Fengli Dai, Junhui Guo, , Pengfei Song,
Published: 5 July 2021
Clay Minerals pp 1-9; https://doi.org/10.1180/clm.2021.23

Abstract:
Montmorillonite (Mnt), a clay mineral with a nanolayered structure, was combined with an Fe-based metal–organic framework (MOF; MIL-53(Fe)) using an in situ growth technique that yielded a novel eco-friendly clay-based adsorbent (MIL-53(Fe)@Mnt). The adsorbent was characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis and N2 gas adsorption. The MIL-53(Fe) particles grew on the surface of the nanolayered Mnt and the MIL-53(Fe) particle size became smaller. The adsorption performance of MIL-53(Fe)@Mnt was investigated by removing methylene blue (MB), and optimization experiments were carried out to study the effects of contact time, pH, initial dye concentration and adsorbent mass on the adsorption processes. The MIL-53(Fe)@Mnt exhibited excellent adsorption capacity for MB, namely 313.7 mg g−1, which was 3.02 times and 3.54 times greater than that of pure Mnt and MIL-53(Fe), respectively. Adsorption was fitted with the Langmuir isotherm model and followed a pseudo-second order kinetic model. The MIL-53(Fe)@Mnt obtained is a low-cost and eco-friendly adsorbing material and might be a candidate for removing dyes during water treatment.
, Cristian Biagioni, Luboš Vrtiška, Yves Moëlo
Mineralogical Magazine pp 1-9; https://doi.org/10.1180/mgm.2021.57

Abstract:
The new mineral, zvěstovite-(Zn), ideally Ag6(Ag4Zn2)As4S13, was found in quartz–baryte gangue at the mine dump of the abandoned small deposit of Zvěstov, central Bohemia, Czech Republic. Zvěstovite-(Zn) is associated with tennantite-(Zn), tetrahedrite-(Zn), argentotennantite-(Zn), acanthite and supergene azurite and malachite. The new mineral occurs as rare relic anhedral grains rimmed by acanthite, up to 100 μm in size. Zvěstovite-(Zn) is grey, Mohs hardness is ca. 3½–4, in agreement with other members of the tetrahedrite group; the calculated density is 5.16 g.cm–3. In reflected light, zvěstovite-(Zn) is grey with a greenish tint, without bireflectance, pleochroism or anisotropy. Deep red internal reflections are ubiquitous. Reflectance values of zvěstovite-(Zn) in air (R%) are: 28.5 at 470 nm, 26.9 at 546 nm, 25.5 at 589 nm and 23.8 at 650 nm. The empirical formula for zvěstovite-(Zn), based on electron-microprobe analyses (n = 4), is Ag6.27[(Ag3.90Cu0.38)Σ4.28(Zn1.60Fe0.09Cd0.03)Σ1.72]Σ6.00(As2.26Sb1.48)Σ3.74S12.50. The ideal formula is Ag6(Ag4Zn2)As4S13, which requires (in wt.%) Ag 56.01, Zn 6.79, As 15.56 and S 21.64, total 100.00. Zvěstovite-(Zn) is cubic, I $\bar{4}$ 3m, with unit-cell parameters: a = 10.850(2) Å, V = 1277.3(8) Å3 and Z = 2. The strongest reflections of the calculated powder X-ray diffraction pattern [d, Å (I) (hkl)] are: 3.1321(100) (222), 2.7125(21) (400), 1.9809(11) (521), 1.9180(31) (440) and 1.6357(15) (622). According to the single-crystal X-ray diffraction data (R obs = 0.051), the crystal structure of zvěstovite-(Zn) agrees with the general features of the members of the tetrahedrite group. Zvěstovite-(Zn) is named after its type locality, Zvěstov; the suffix indicates the dominant divalent C-constituent, according to the approved nomenclature of the tetrahedrite group. It is the As-isotype of rozhdestvenskayaite-(Zn). The mineral and its name have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA2020-061).
Chunguang Xiao, Feng Lang, Yu Xiang, Yi Lin,
Published: 2 July 2021
Clay Minerals pp 1-12; https://doi.org/10.1180/clm.2021.22

Abstract:
Modified sericite mica was prepared by combining the intercalation of cetyltrimethylammonium bromide (CTAB) through ion exchange and surface modification of 3-aminopropyltriethoxysilane (KH550) with the following steps: high-temperature activation of sericite mica, acid activation, sodium modification, LiNO3 treatment, the ion-exchange intercalation of the cetyltrimethylammonium cation (CTA+) and surface modification of KH550. High-temperature activation was the most critical step for the modified sericite mica, and the number of hydroxyl groups of mica under high temperature directly affected the surface modification of KH550. The effects of various activation temperatures on the surface modification of sericite mica were investigated. The structure of activated sericite mica was intact when activation temperature was 600°C or 700°C, and the surface modification of sericite mica was not affected. The structure of activated sericite mica was partially destroyed at 800°C. The optimal temperature for activating sericite mica was 700°C. The structure and morphology of modified sericite mica were characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, Brunauer–Emmett–Teller (BET) analysis and loose bulk volume. The KH550 could not only chemically graft onto the surface of sericite mica, but also enter into the interlayer through electrostatic attraction after its end amino group was protonated. The interlayer spacing of modified sericite mica increased to 3.22 nm, indicating that it might be an excellent layered silicate for preparing clay–polymer nanocomposites.
Maria A. Sitnikova, Vicky Do Cabo, Frances Wall, Simon Goldmann
Mineralogical Magazine pp 1-18; https://doi.org/10.1180/mgm.2021.56

Abstract:
The Neoproterozoic Lofdal alkaline carbonatite complex consists of a swarm of carbonatite dykes and two plugs of calcite carbonatite known as the ‘Main’ and ‘Emanya’ carbonatite intrusions, with associated dykes and plugs of phonolite, syenite, rare gabbro, anorthosite and quartz-feldspar porphyry. In the unaltered Main Intrusion calcite carbonatite the principal rare-earth host is burbankite. As burbankite typically forms in a magmatic environment, close to the carbohydrothermal transition, this has considerable petrogenetic significance. Compositional and textural features of Lofdal calcite carbonatites indicate that burbankite formed syngenetically with the host calcite at the magmatic stage of carbonatite evolution. The early crystallisation of burbankite provides evidence that the carbonatitic magma was enriched in Na, Sr, Ba and light rare earth elements. In common with other carbonatites, the Lofdal burbankite was variably affected by alteration to produce a complex secondary mineral assemblage. Different stages of burbankite alteration are observed, from completely fresh blebs and hexagonal crystals through to complete pseudomorphs, consisting of carbocernaite, ancylite, cordylite, strontianite, celestine, parisite and baryte. Although most research and exploration at Lofdal has focused on xenotime-bearing carbonatite dykes and wall-rock alteration, this complex also contains a more typical calcite carbonatite enriched in light rare earth elements and their alteration products.
E.P. Reguir, E.B. Salnikova, P. Yang, A.R. Chakhmouradian, M.V. Stifeeva, I.T. Rass, A.B. Kotov
Mineralogical Magazine pp 1-45; https://doi.org/10.1180/mgm.2021.53

, Victor N. Yakovenchuk, Nataliya Yu. Yanicheva, Yakov A. Pakhomovsky, Vladimir V. Shilovskikh, Vladimir N. Bocharov, Sergey V. Krivovichev
Mineralogical Magazine pp 1-13; https://doi.org/10.1180/mgm.2021.51

Abstract:
Microporous slicates with the pharmacosiderite structure and the general formula A 3–x H1+x [Ti4O4(SiO4)3](H2O) n (A = Na, K, Cu), (n = 6–9, x = 0–2) are outstanding in their ion-exchange properties. The ivanyukite mineral group consists of three species, one of which has two polymorphs. The minerals forming a progressive series: ivanyukite-Na-T → ivanyukite-Na-C → ivanyukite-K → Cu-rich ivanyukite-K → ivanyukite-Cu, have been studied by single-crystal X-ray diffraction, electron microprobe analysis and Raman spectroscopy. The microporous heteropolyhedral framework of the ivanyukite-group minerals is based on cubane-like [Ti4O4]8+ clusters that share common corners with SiO4 tetrahedra to form wide three-dimensional channels suitable for the migration of Na+, K+ and Cu2+ ions. Ivanyukite-Na-T that has a R3m symmetry loses Na+ in aqueous solutions via the substitution Na+ + O2‒ ↔ □ + OH‒, which allows for the migration of K+ ions and transformation of initial structure into the cubic (P $\bar{4}3m$ ) ivanyukite-Na-C polymorph or into ivanyukite-K, when most of Na is lost. Natural ivanyukite-Na-C is shown to contain domains of both R3m (subordinate) and P $\bar{4}3m$ (dominant) symmetry with the chemical composition determining the stability and dominance of cubic or trigonal forms. Incorporation of Cu into the crystal structure ivanyukite-K via the substitution K+ + OH− ↔ Cu2+ + O2− in aqueous solutions results in the formation of ivanyukite-Cu. Post-crystallisation processes (such as exchange of Na+, K+, Cu2+, and/or hydration/dehydration of primary phases) are widespread in hyperagpaitic rocks of the Kola alkaline massif and the respective mineral transformations contribute to the diversity of mineral species.
, Natalia V. Zubkova, Atali A. Agakhanov, Vasiliy O. Yapaskurt, Dmitry I. Belakovskiy, Marina F. Vigasina, Sergey N. Britvin, Anna G. Turchkova, Evgeny G. Sidorov, Dmitry Yu. Pushcharovsky
Mineralogical Magazine pp 1-10; https://doi.org/10.1180/mgm.2021.47

Abstract:
The new mineral yurgensonite, ideally K2SnTiO2(AsO4)2, the first natural arsenate with species-defining tin, and the continuous isomorphous series between yurgensonite and katiarsite KTiO(AsO4) are described from sublimates of the Arsenatnaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. Yurgensonite and a Sn-bearing variety of katiarsite are associated closely with one another and with badalovite, pansnerite, yurmarinite, achyrophanite, arsenatrotitanite, hatertite, khrenovite, svabite, sanidine, hematite, cassiterite, rutile and aphthitalite-group sulfates. Yurgensonite occurs as sword-shaped crystals up to 0.01 mm × 0.05 mm × 1 mm or acicular to hair-like individuals up to 1 mm long, typically forming radial aggregates up to 2 mm across. It is transparent, colourless, white or pale beige, with vitreous lustre. The mineral is brittle, cleavage was not observed. D calc is 3.877 g cm-3. Yurgensonite is optically biaxial (–), α = 1.764(6), β = 1.780(6), γ = 1.792(6) and 2Vmeas. is large. Chemical composition (wt.%, electron-microprobe; holotype) is: Na2O 0.51, K2O 16.27, Rb2O 0.12, Al2O3 0.26, Fe2O3 4.33, SiO2 0.29, TiO2 10.17, SnO2 22.01, P2O5 0.14, V2O5 0.19, As2O5 40.20, Sb2O5 4.88, SO3 0.28, total 99.65. The empirical formula based on 10 O apfu is (K1.92Na0.09Rb0.01)Σ2.02(Sn0.81Ti0.71Fe3+ 0.30Sb5+ 0.17Al0.03)Σ2.02(As1.945Si0.03S0.02P0.01V0.01)Σ2.015O10. Yurgensonite is orthorhombic, Pna21, a = 13.2681(6), b = 6.6209(3), c = 10.8113(5) Å, V = 949.74(7) Å3 and Z = 4. The crystal structure was solved from single-crystal X-ray diffraction data, R = 5.02%. Yurgensonite belongs to the KTP-structure type. It is a Ti,Sn-ordered analogue of katiarsite. The structure contains chains of corner-linked alternating crystallographically non-equivalent octahedra M(1) and M(2). In yurgensonite, Sn4+ prevails in the M(2)O6 octahedron whereas the M(1) site is Ti4+-dominant. The new mineral is named in honour of the Russian mineralogist, geochemist and specialist in studies of ore deposits Professor Georgiy Aleksandrovich Yurgenson (born 1935).
, Ljiljana Karanović
Mineralogical Magazine pp 1-15; https://doi.org/10.1180/mgm.2021.41

Abstract:
We report on the crystal structures of three novel synthetic SrM-arsenates (M = Ni and Fe3+), isostructural or structurally related to the minerals from tsumcorite, carminite and brackebuschite groups. They were synthesised under mild hydrothermal conditions and further characterised using single-crystal X-ray diffraction (SXRD), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) and Raman spectroscopy. SXRD and SEM-EDS yielded formulae: (I) SrNi2(AsO4)2⋅2H2O, (II) Sr1.4Fe3+ 1.6(AsO4)2(OH)1.6 and (III) SrFe3+(AsO4)(AsO3OH). All three structures are built up of slightly distorted MO6 octahedra and AsO4 tetrahedra that are linked by Sr2+ with different coordination geometries and hydrogen bonds. I represent a basic structure type typical for tsumcorite-group minerals (space group C2/m) while II has a new intermediate structure between carminite, PbFe3+ 2(AsO4)2(OH)2 and arsenbrackebuschite, Pb2Fe3+(AsO4)2(OH) (s.g. Pm). III is triclinic and adopts a new structure-type (s.g. P $\bar{1}$ ). The structure of I is built up of infinite linear edge-sharing NiO4(OH2)2 octahedral chains, extending along [010] and linked by AsO4 tetrahedra, SrO8 polyhedra and hydrogen bonds. The structure of II is characterised by the carminite-like FeO4(OH)2 octahedral chains and Edshammar-polyhedral chains, which involves SrO11 coordination polyhedra similar to that of PbO11 in arsenbrackebuschite. Both chains in II are aligned parallel to the b axis of the monoclinic unit cell and connected together by the arsenate AsO4 tetrahedra, SrO8 polyhedra and the hydrogen-bonding network. The compound III has a new type of crystal structure based on the unusual corrugated octahedral–tetrahedral-quadruple chains. These are made up of a central double-sided chain linked to two single-sided chains into a quadruple chain extended along the a axis. The chains in III are built up of FeO6 octahedra and AsO4 tetrahedra further linked to each other by shared vertices. The quadruple chains are interconnected by additional AsO4 tetrahedra forming a heteropolyhedral 3D open framework. Strontium atoms are situated in the two channels. The structural connections to related minerals and inorganic compounds are discussed.
Emil Aarestrup, , Paul E.B. Armitage, Allen P. Nutman, Ole Christiansen,
Mineralogical Magazine pp 1-25; https://doi.org/10.1180/mgm.2021.44

Abstract:
Whole-rock major- and trace-element data are presented on a sample collection from the >3 Ga Amikoq Layered Complex (ALC), and hosting amphibolites within the Mesoarchean Akia terrane, SW Greenland. The lithologies range from leuconorite to melanorite/feldspathic orthopyroxenite, orthopyroxenite to harzburgite through to dunite, and tholeiitic basaltic–picritic mafic host rocks. The Amikoq Layered Complex samples are primitive (Mg#: 65–89) with elevated Ni and Cr contents. However, the absence of troctolitic lithologies and the presence of two orthopyroxene compositional trends, suggests that the successions might not be comagmatic. On the basis of trace-element cumulate models, relatively low Ni contents and minor negative Sr-Eu anomalies in some high-Ti ultramafic rocks, it is not possible to exclude a petrogenesis related to a melt similar to that of the mafic host-rocks. Ultramafic samples with U-shaped trace-element distribution patterns are petrogenetically related to the noritic sequences, either through cumulus mineral accumulation or melt-rock reactions. Assimilation-fractional-crystallisation modelling of melanorites nevertheless require the parental melt to have been contaminated/mixed with a component of island-arc-like tholeiite affinity. A boninite-like parental melt might have been derived from the subcontinental lithospheric mantle of the Akia terrane, or alternatively via assimilation of an ultramafic parental melt with island-arc-like tholeiite. Given the complex geological evolution and high-grade metamorphic overprint of the Amikoq Layered Complex, we are unable to differentiate between the two models.
Mineralogical Magazine pp 1-30; https://doi.org/10.1180/mgm.2021.43

Abstract:
Several text symbol lists for common rock-forming minerals have been published over the last 40 years, but no internationally agreed standard has yet been established. This contribution presents the first International Mineralogical Association (IMA) Commission on New Minerals, Nomenclature and Classification (CNMNC) approved collection of 5744 mineral name abbreviations by combining four methods of nomenclature based on the Kretz symbol approach. The collection incorporates 991 previously defined abbreviations for mineral groups and species and presents a further 4753 new symbols that cover all currently listed IMA minerals. Adopting IMA–CNMNC approved symbols is considered a necessary step in standardising abbreviations by employing a system compatible with that used for symbolising the chemical elements.
, Mark D. Welch, John Spratt, Annette K. Kleppe, Martin Števko
Mineralogical Magazine pp 1-8; https://doi.org/10.1180/mgm.2021.40

Abstract:
The occurrence, chemical composition and structural characterisation of the new mineral kernowite, ideally Cu2Fe(AsO4)(OH)4⋅4H2O, the Fe3+-analogue of liroconite, Cu2Al(AsO4)(OH)4⋅4H2O, are described. Kernowite (IMA2020-053) occurs on specimens probably sourced from the Wheal Gorland mine, St Day, Cornwall, UK, in the cavities of a quartz-gossan rich in undifferentiated micro-crystalline grey sulfides and poorly crystalline arsenic phases including both pharmacosiderite and olivenite-group minerals. The average composition of kernowite determined from several holotype fragments by electron microprobe analysis is Cu1.88(Fe0.79Al0.09)Σ0.88(As1.12O4)(OH)4⋅3.65H2O. The structure of kernowite has been determined in monoclinic space group I2/a (a non-standard setting of C2/c) by single-crystal X-ray diffraction (SCXRD) to R 1 = 0.025, wR 2 = 0.051 and Goodness-of-fit = 1.112. Unit-cell parameters from SCXRD are a = 12.9243(4) Å, b = 7.5401(3) Å, c = 10.0271(3) Å, β = 91.267(3)°, V = 976.91(6) Å3 and Z = 4. The chemical formula of this crystal indicated by SCXRD from refined site-scattering is Cu2(Fe3+ 0.84(1)Al0.16)AsO4(OH)4⋅4H2O. The network of hydrogen bonding has been determined and is similar to that reported for liroconite from Wheal Gorland by Plumhoff et al. (2020).
, Emil Holtung Gulbransen,
Mineralogical Magazine pp 1-7; https://doi.org/10.1180/mgm.2021.42

Abstract:
A nomenclature scheme has been set up for the nordite supergroup of minerals, which have the general formula A 2 BXYZT 6O17 and where A = Na; B = Na, Ca; X = Sr, Ca, Ba; Y = REE, Sr; Z = Zn, Fe, Mn, Mg and T = Si. The nordite supergroup includes nordite-(La), nordite-(Ce), ferronordite-(La), ferronordite-(Ce) and manganonordite-(Ce), as well as meieranite which is considered as an unassigned member of the nordite supergroup. In the known nordite-group minerals the Y site is occupied by rare earth elements (REE), while in meieranite the Y site is occupied by Sr. The dominant element on the tetrahedral Z site determines the prefix used in the mineral name. New rootnames must be given to species with a different dominant element on the A, B or X sites. Nordite supergroup minerals are orthorhombic, although nordite-group minerals and meieranite crystallise in the Pcca and P21 nb space groups, respectively. The proposed nomenclature scheme for the nordite supergroup has been approved by the Commission on New Minerals, Nomenclature and Classification (CNMNC) of the International Mineralogical Association (IMA). In addition, new chemical and structural investigations were performed on nordite-(Ce) from Illutalik (Igdlutalik), South Greenland, leading to the first crystal structure refinement for nordite-(Ce).
Published: 19 April 2021
Mineralogical Magazine pp 1-10; https://doi.org/10.1180/mgm.2021.39

Abstract:
Myrmekites occurring in monzodiorite from the Meichuan pluton in the Dabie ultrahigh-pressure metamorphic belt were investigated. The petrographic evidence demonstrates a metasomatic origin for myrmekite formation at the scale of individual alkali feldspar grains, and that the myrmekitic quartz and plagioclase matrix are generated simultaneously replacing precursor feldspar. Energy-dispersive X-ray spectroscopy and electron microprobe analysis indicate a low anorthite content in the narrow rim of host plagioclase near the myrmekite–alkali-feldspar interface. The Ca2+, Na+ proportion of hydrothermal fluids replacing precursor alkali feldspar is 1:5.4, calculated from the anorthite content of the inner part of the host plagioclase and the neighbouring alkali feldspar. Electron back-scattered diffraction was used to identify the crystallographic orientation of the myrmekitic quartz, plagioclase matrix and the precursor alkali feldspar. The crystallographic orientation relationships (110)Kfs//(11 $\bar{2}\bar{1}$ )Qtz, (20 $\bar{1}$ )Kfs//(11 $\bar{2}$ 1)Qtz and [11 $\bar{2}3]$ Qtz//[001]Kfs between myrmekitic quartz and adjacent alkali feldspar were obtained from statistical analysis. No clear crystallographic orientation relationship between quartz and plagioclase was found. The growth of myrmekitic quartz is constrained by the precursor alkali feldspar rather than the simultaneously crystallised plagioclase. This research is helpful for understanding the intergrowth mechanism during metasomatism.
, Mario Luiz De Sá Carneiro Chaves, Rosaline Cristina Figueiredo e Silva, Sylvio Dutra Gomes
Published: 19 April 2021
Mineralogical Magazine pp 1-16; https://doi.org/10.1180/mgm.2021.38

Abstract:
Fluid-inclusion studies were conducted on amethyst quartz from three different geological environments: basalt cavities; hydrothermal veins; and granitic pegmatites of Eastern Brazil, to understand the conditions of amethyst crystallisation in each of these environments. In samples from basalt cavities, fluid inclusions are exclusively one-phase aqueous types suggesting a low-temperature formation environment. Crystals from the two other environments show that fluid inclusions can be either one-phase aqueous, two-phase aqueous, three-phase aqueous carbonic, or three-phase aqueous with the presence of precipitated solid halite. The carbonic composition of the system H2O–CO2–NaCl was confirmed by Raman spectroscopic analysis and suggests a metamorphic or magmatic fluid source. Fluid inclusions trapped in samples from hydrothermal veins reveal at least two different fluid generations based on homogenisation temperatures. The first generation has minimum trapping temperatures between 249°C and 391°C. The second generation of lower temperature fluids has minimum trapping temperatures varying from 82°C to 203°C. Fluid inclusions of this group record eutectic temperatures that indicate the presence of Ca and Fe cations in addition to Na. Fluid inclusions trapped in amethyst from a pegmatite body have moderate salinity values between 15 and 25 eq. wt.% NaCl, thus reflecting the elevated salt content in pegmatite-forming fluids. In this sample, the first fluid generation is represented by aqueous fluid inclusions with minimum trapping temperatures ranging from 268°C to 375°C. The estimated eutectic temperatures, generally below –50°C, indicate the presence of Ca cations in addition to Na. Minimum trapping temperatures correspond to temperatures of late-to-post-pegmatitic hydrothermal stages. The second generation records minimum trapping temperatures between 125°C and 247°C. Amethyst from both hydrothermal veins and pegmatite environments contain solid inclusions of hematite, an indication that the mineralising fluid was Fe rich and thus, possibly magmatic in origin.
Peter Elliott, , Anthony C. Willis
Published: 14 April 2021
Mineralogical Magazine pp 1-6; https://doi.org/10.1180/mgm.2021.36

Abstract:
Aldermanite from Tom's quarry in the Kapunda–Angaston area of the Mount Lofty Ranges, South Australia has been characterised by electron microprobe analyses and single-crystal structure analysis. The empirical formula is Na0.72K0.13Ca0.06Mg1.15Al2.92(PO4)2.05[(OH)2.92F2.96]Σ5.88⋅8.91H2O, based on 23 anions. Analysis of a specimen from the type locality, the nearby Klemm's quarry, Moculta, gave a similar formula, Na0.59K0.06Ca0.36Mg0.92Al3.16(PO4)1.97[(OH)4.08F2.70]Σ6.78⋅8.36H2O. Na and F were not analysed in the original description of the mineral. The ideal end-member formula is [Mg(H2O)6][Na(H2O)2Al3(PO4)2(OH)6]⋅H2O, compared to the original formula of Mg5Al12(PO4)8(OH)22⋅nH2O with n ≈ 32. Aldermanite is monoclinic, P21/c with a = 13.524(3), b = 9.958(2), c = 7.013(1) Å and β = 97.40(3)°. The crystal structure of aldermanite is built from sawtooth layers of cis- and trans-corner-connected, Al-centred octahedra, decorated with corner-connected PO4 tetrahedra to give (100) layers of composition Al3(PO4)2(OH,F)6. Interlayer Mg(H2O)6 octahedra and H2O molecules hold the layers together through H bonding. The corner-connected octahedra form 6-membered rings that are centred by 8-coordinated Na and have a topology identical to a 3-octahedra-wide {110} slice of the pyrochlore structure. This pyrochlore element contains intersecting kagomé nets of Al atoms, parallel to (111) and (11 $\bar{1}$ ) of cubic pyrochlore. Minerals of the walentaite group, as well as zirconolite-3O polytypes have the same type of intersecting kagomé nets of small cations.
Monojit Dey, Sourav Bhattacharjee, Aniket Chakrabarty, Roger H. Mitchell, Supriyo Pal, Supratim Pal, Amit Kumar Sen
Published: 14 April 2021
Mineralogical Magazine, Volume 85, pp 588-606; https://doi.org/10.1180/mgm.2021.37

Abstract:
Pyrochlore-group minerals are common in the Neoproterozoic Sevattur carbonatite complex. This complex is composed of dolomite-, calcite-, banded- and blue carbonatite together with pyroxenite, albitite and diverse syenites. This work reports the paragenetic-textural types and compositional variation of pyrochlore hosted by dolomite carbonatite, banded carbonatite and albitite together with that of alteration assemblages containing belkovite and baotite. On the basis of composition, five different types of pyrochlore are recognised and termed Pcl-I through to Pcl-V. The Pb-rich Pcl-I are present exclusively as inclusions in U-rich Pcl-IIa in dolomite carbonatite. The alteration assemblages of Pb-poor Pcl-IIb + Ba-rich or Ba–Si- rich Pcl-IV + belkovite (dolomite carbonatite) and Si-rich Pcl-V + baotite (banded carbonatite) formed after Pcl-IIa differ in these carbonatites. The albitite hosts extremely U-Ti-rich Pcl-III, mantled by Ba-rich potassium feldspar. In common with the banded carbonatite, Pcl-V is formed by alteration of Pcl-III where this mantle is partially, or completely broken. The Ba-Si-enrichment of Pcl-IV and Pcl-V together with the ubiquitous presence of baryte in all Sevattur lithologies suggests late-stage interaction with a Ba-Si-rich acidic hydrothermal fluid. This fluid was responsible for leaching silica from the associated silicates and produced Pcl-V in the silicate-rich lithologies of the banded carbonatite and albitite. The absence of Pcl-V in dolomite carbonatite is a consequence of the low modal abundance of silicates. The complex compositional diversity and lithology specific pyrochlore alteration assemblages suggest that all pyrochlore (Pcl-I to Pcl-IV) were formed initially in an unknown source and transported subsequently in their respective hosts as altered antecrysts.
, Robert Bolhar, Lunga Bam, Bradley M. Guy, Grant M. Bybee, Paul A. M. Nex
Published: 31 March 2021
Mineralogical Magazine pp 1-18; https://doi.org/10.1180/mgm.2021.32

Abstract:
Copper-sulfides within carbonatites and phoscorites of the Phalaborwa Igneous Complex, South Africa, have been investigated since the middle of the 20th Century. However, aspects of ore formation have remained unclear. This study examines the mechanisms involved in Cu-sulfide mineralisation by micro-focus X-ray computed tomography as applied to sulfide-rich drill core samples. Several texturally distinct assemblages of magmatic sulfides can be identified, including: (1) <500 μm rounded bornite and chalcopyrite grains disseminated within the gangue; (2) elongated mm-scale assemblages of chalcopyrite and bornite; and (3) mm-to-cm thick chalcopyrite cumulates. Chalcopyrite veins were also observed, as well as late-stage valleriite, documenting late-stage fluid circulation within the pipe, and alteration of magmatic and hydrothermal sulfides along fractures within the gangue, respectively. The results of micro-focus X-ray computed tomography indicate that magmatic sulfides are sub-vertically aligned. Spatial variability of the sulfide assemblages suggests that textural changes within sulfide layers reflect fluctuating magma flow rate during emplacement of carbonatite–phoscorite magmas, through coalescence or breakup of sulfide liquid droplets during ascent. Modal sulfide abundances, especially for disseminated assemblages, differ from one carbonatite–phoscorite layer to another, suggesting a strong control of the mechanical sorting in the formation of Cu-sulfide textures within the Loolekop carbonatite. The alternation of carbonatite and phoscorite within the intrusion suggest that the Loolekop Pipe was emplaced through a series of successive magma pulses, which differentiated into carbonatite and phoscorite by melt immiscibility/progressive fractional crystallisation and pressure drop. Three-dimensional textural analysis represents an effective tool for the characterisation of magma flow and is useful for the understanding of magmatic processes controlling sulfide liquid-bearing phoscorite–carbonatite magmas.
, Jakub Plášil, Travis A. Olds, Barbara P. Nash, Joe Marty
Published: 31 March 2021
Mineralogical Magazine pp 1-6; https://doi.org/10.1180/mgm.2021.33

Abstract:
The new mineral uranoclite (IMA2020-074), (UO2)2(OH)2Cl2(H2O)4, was found in the Blue Lizard mine, San Juan County, Utah, USA, where it occurs as tightly intergrown aggregates of irregular yellow crystals in a secondary assemblage with gypsum. The streak is very pale yellow and the fluorescence is bright green–white under 405 nm ultraviolet light. Crystals are translucent with vitreous lustre. The tenacity is brittle, the Mohs hardness is ~1½, the fracture is irregular. The mineral is soluble in H2O and has a calculated density of 4.038 g⋅cm–3. Electron microprobe analyses provided (UO2)2(OH)2.19Cl1.81(H2O)4. The six strongest powder X-ray diffraction lines are [d obs Å(I)(hkl)]: 8.85(38)(002), 5.340(100)(200, 110), 5.051(63)( $\bar{2}$ 02), 4.421(83)(112, 004, 202), 3.781(38)( $\bar{2}$ 12) and 3.586(57)(014, $\bar{2}$ 04). Uranoclite is monoclinic, P21/n, a = 10.763(8), b = 6.156(8), c = 17.798(8) Å, β = 95.656(15)°, V = 1173.5(18) Å3 and Z = 4. The structure is the same as that of synthetic (UO2)2(OH)2Cl2(H2O)4 in which the structural unit is a dimer consisting of two pentagonal bipyramids that share an equatorial OH–OH edge. The dimers are linked to one another only by hydrogen bonding. This is the second known uranyl mineral containing essential Cl and the first in which Cl coordinates to U6+.
, Ralph Rowe, Glenn Poirier, Gerald Giester, Kate Helwig
Published: 31 March 2021
Mineralogical Magazine pp 1-8; https://doi.org/10.1180/mgm.2021.31

Abstract:
The new högbomite-group mineral magnesiohögbomite-6N12S, ideally Mg5Al11TiO23(OH), was found in calcite “vein-dikes” at the DeWitts Corners occurrence, lots 10 and 11, concession 1, Bathurst Township, Ontario, Canada. It forms tabular and short-prismatic crystals up to 5 mm in size. The major forms are pinacoid {0001} and hexagonal pyramid {11 ${\bar 2}$ 1}, sometimes modified by hexagonal prism {11 ${\bar 2}$ 0}. The associated minerals are magnesiohögbomite-2N3S, spinel, corundum, diopside, magnesio-hastingsite, pargasite, clinochlore and calcite. Magnesiohögbomite-6N12S is dark brown to black with brown streak and vitreous lustre. It has no cleavage and its fracture is uneven. The Mohs hardness is 6½. D calc is 3.87 g/cm3. The infrared spectrum is reported. The composition (wt.%) is MgO 13.09, ZnO 0.46, FeO 11.91, Fe2O3 6.84, Al2O3 62.70, TiO2 4.44, H2O 0.99, total 100.43. The empirical formula calculated on the basis of 17 cations, excluding H+, is (Mg2.95Fe2+ 1.51Al0.49Zn0.05)Σ5(Al10.71Fe3+ 0.78Ti0.51)Σ12O23(OH). The simplified formula is (Mg,Fe)5(Al,Fe,Ti)12O23(OH). The mineral is trigonal, R ${\bar 3}$ m, a = 5.7194(2), c = 83.069(5) Å, V = 2353.3(2) Å3 and Z = 6. The strongest reflections of the powder X-ray diffraction pattern [d,Å(I)(hkl)] are: 2.921(26)(0.1.23), 2.863(49)(110), 2.687(29)(0.1.26), 2.547(31)(0.1. $\overline{28}$ ) and 2.434(100)(1.1.18). The crystal structure was solved and refined from single-crystal X-ray diffraction data to R 1 = 0.022. It is composed of alternating spinel (S) and nolanite (N) modules in the sequence 3 × (NSSNSS). The sequence of cubic ‘c’ and hexagonal ‘h’ closed-packed oxygen layers is 3 × (cccccchcccch). It is the first polysome in the högbomite supergroup with such a sequence.
Chen Wei, , Zhilong Huang, , Haoyu Wang
Published: 26 March 2021
Mineralogical Magazine pp 1-15; https://doi.org/10.1180/mgm.2021.29

Abstract:
Zoning texture in sphalerite has been described in many studies, although its genesis and ore formation process are poorly constrained. In this investigation, we compare the in situ trace element and isotopic composition of colour-zoned sphalerites from Nayongzhi, South China, to explain the zoning growth process. Petrographic observations identified two broad types of zoned sphalerite, core–rim (CR) and core–mantle–rim (CMR) textures. Each zoned sphalerite displays two or three colour zones, including brown core, light colour bands and/or pale-yellow zones. In situ laser ablation inductively coupled plasma mass spectrometry trace-element analyses show that the three colour zones display variable trace-element compositions. Brown cores exhibit distinctly high Mn, Fe, Co, Ge, Tl and Pb concentrations, whereas pale-yellow and light colour zones have elevated Ga, Cd, Sn, In and Sb concentrations. Copper, Sb, In and Sn show slight variations between pale-yellow and light zones, the latter having higher In and Sn, but lower Cu and Sb abundances. Given the low concentration range of Pb, Ge, Tl, Mn Sb, Cd, etc., the colour of sphalerite is attributed mainly to Fe compositional variation. The δ34S values of sphalerite from Nayongzhi range from +22.3 to +27.9‰, suggesting reduced sulfur was generated by thermochemical sulfate reduction of marine sulfate in ore-hosted strata. Single-crystal colour-zoned sphalerite exhibits intracrystalline δ34S variation (up to 4.3‰), which is attributed to the δ34S composition of H2S in the original fluid. The lack of correlation between trace elements and δ34S values indicates episodic ore solution influxes and mixes with the reduced sulfur-rich fluid derived from the aquifers of the ore-hosted strata, which play a key role in the formation of the zoned Nayongzhi sphalerite. In conclusion, in situ trace element and S isotope studies of zoned sphalerite crystals might provide insight into the ore-forming process of MVT deposits.
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