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Cluster of calcinaksite crystals in a fine-grained aggregate of calcium hydrosilicates. Photo: Fred Kruijen
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The new mineral calcinaksite, ideally KNaCa(Si4O10) · H2O, the first hydrous and Ca-dominant member of the litidionite group, is found in a xenolith of metamorphosed carbonate-rich rock from the southern lava flow of the Bellerberg volcano, Eastern Eifel region, Rheinland-Pfalz, Germany. It is associated with wollastonite, gehlenite, brownmillerite...
Citations
... The differences in the degree of conversion can be caused by many factors, such as: various temperatures of the magma; different cooling rates; different levels of water vapour and other volatile substances (fluorine, chlorine and sulfur); different sizes of xenoliths; and multiple heating of xenoliths and/or prolonged exposure to escaping hot gases or by lava entering the environment (Hentschel, 1987). Moreover, the xenoliths from Bellerberg volcano are known for their diversity of secondary, low-temperature phases and the source of several new mineral species (Abraham et al., 1983;Irran et al., 1997;Mihajlovic et al., 2004;Chukanov et al., 2012Chukanov et al., , 2015Galuskin et al., 2016;Juroszek et al., 2018). ...
The recently defined arctite supergroup contains nine mineral members defined as hexagonal intercalated antiperovskites, most of which have been found in pyrometamorphic rocks of the Hatrurim Complex, Israel. Three members of this supergroup: nabimusaite, gazeevite and zadovite, were identified for the first time in altered carbonate–silicate xenoliths from the Caspar and Scherer quarries, Bellerberg volcano in Germany. Present work focuses on the chemical, structural and spectroscopic investigation of these minerals and their correlation with holotype counterparts. The apparent differences are mainly related to the chemical composition, types of substitution in the tetrahedral and antiperovskite layers within the crystal structure, and position of bands in the Raman spectra. In the Bellerberg volcano xenoliths, the crystallisation of nabimusaite and gazeevite is caused by high-temperature alteration of early mineral associations (clinker-like phases) and their reaction with melt or gas generated by volcanic activity. In turn, the formation of zadovite is related to the Ba-rich silicate melt that filled the intergranular space between the rock-forming minerals.
... Litidionite is a rare Cu-Na-K-bearing silicate, first discovered at the Somma-Vesuvius volcano, Italy (Scacchi, 1880). At present, the litidionite group contains four minerals: litidionite, CuKNaSi 4 O 10 (Pozas et al., 1975), manaksite, MnKNaSi 4 O 10 (Khomyakov et al., 1992), fenaksite, Fe 2+ KNaSi 4 O 10 (Rozhdestvenskaya et al., 2004) and calcinaksite, CaKNaSi 4 O 10 ⋅H 2 O (Chukanov et al., 2015). The litidionite-bearing assemblage is typical of high-temperature alteration processes at the rockfumaroles interface (Pozas et al., 1975;Balassone et al., 2019). ...
... Synthetic analogues of litidionite, manaksite and fenaksite have been obtained under hydrothermal conditions and 230°C (Brandão et al., 2009). Recently, Chukanov et al. (2015) described an H 2 O-bearing litidionite member calcinaksite. Calcinaksite was first detected in a calcic xenolith hosted by an alkaline basalt at Bellerberg volcano, Eifel, Germany, as the product of contact metamorphism formed during the high-temperature hydrothermal stage (Aksenov et al., 2014;Chukanov et al., 2015). ...
... Recently, Chukanov et al. (2015) described an H 2 O-bearing litidionite member calcinaksite. Calcinaksite was first detected in a calcic xenolith hosted by an alkaline basalt at Bellerberg volcano, Eifel, Germany, as the product of contact metamorphism formed during the high-temperature hydrothermal stage (Aksenov et al., 2014;Chukanov et al., 2015). The second worldwide occurrence of this mineral was recorded at Somma-Vesuvius by Balassone et al. (2019). ...
For this study, the rare Cu-bearing silicate fumarolic assemblages from the Somma–Vesuvius volcano, Italy, characterised by the rare mineral litidionite, CuKNaSi 4 O 10 , were investigated. We report new data about Cu- and Ti-bearing phases found in these mineralisations, in which Ti-bearing litidionite occurs together with kamenevite, perovskite and rutile. Ti-bearing litidionite appears on the latest stages of partial crystallisation of Ti-bearing silica glass. Incorporation of Ti ⁴⁺ into the litidionite crystal structure was investigated in detail. The Raman spectra of Ti-bearing litidionite contains an intense band at 597 cm ⁻¹ related to anti-symmetric bending vibrations of Si‒O bonds or overlapping stretching vibrations of Ti‒O bonds. The bands in the range 350‒500 cm ⁻¹ correspond to symmetric bending vibrations of O‒Si‒O bonds and overlapping stretching vibrations of Ti‒O bonds. The crystal structure of Ti-litidionite has been refined in the P $\bar{1}$ space group, a = 6.9699(7), b = 7.9953(10), c = 9.8227(10) Å, α = 105.186(9), β = 99.458(8) and γ = 114.489(10) to R 1 = 0.064 for 1726 unique observed reflections. The refinement of the site-occupation factors confirmed the presence of Ti at a five-coordinated M site. The mean bond distance of 2.125 Å for the M site agrees with its refined occupancy (Ti 0.32 Cu 0.30 Ca 0.29 Fe 0.09 ) 1.00 . The incorporation of Ti into the litidionite structure is accompanied by the complex heteropolyhedral substitution according to the scheme V Ti ⁴⁺ + VII–VIII □ + IV Al ³⁺ ↔ V Cu ²⁺ + VII-VIII (Na,K) ⁺ + IV Si ⁴⁺ . Two possible configurations for the phase with maximal TiO 2 content (12.06 wt.% or 0.56 Ti apfu) CuTiK□Na 2 Si 7 AlO 20 ( Z = 1) or CuTiK 2 Na□Si 7 AlO 20 ( Z = 1) have been proposed.
... So far, no anhydrous sodium-potassium-calcium silicates have been observed in Nature. However, a number of water-containing minerals such as canasite, (Na,K) 6 Ca 5 Si 12 O 30 (OH,F) 4 , (Rastsvetaeva et al. 2003 (Chukanov et al. 2015) are known from various mineralogically famous regions of the Earth: the Eifel volcanic area (Germany), kimberlite pipes in Kimberley (South Africa) or different Russian localities such as the Khibiny and Lovozero plutons (Kola Peninsula) or the Murun massif (Yakutia). Therefore, it is possible that water-free variants can be found in natural environments as well. ...
In the course of an exploratory study on the quaternary system Na2O-K2O-CaO-SiO2 single crystals of the first anhydrous sodium potassium calcium silicate have been obtained from slow cooling of a melt in the range between 1250 and 1050 °C. Electron probe micro analysis suggested the following idealized molar ratios of the oxides for the novel compound: K2O:Na2O:CaO:SiO2 = 1:1:12:8 (or KNaCa6Si4O15). Single-crystal diffraction measurements on a crystal with chemical composition K1.08Na0.92Ca6Si4O15 resulted in the following basic crystallographic data: monoclinic symmetry, space group P 21/c, a = 8.9618(9) Å, b = 7.3594(6) Å, c = 11.2453(11) Å, β= 107.54(1)°, V = 707.2(1) Å3, Z = 2. Structure solution was performed using direct methods. The final least-squares refinement converged at a residual of R(|F|) = 0.0346 for 1288 independent reflections and 125 parameters. From a structural point of view, K1.08Na0.92Ca6Si4O15 belongs to the group of mixed-anion silicates containing [Si2O7]- and [SiO4]-units in the ratio 1:2. The mono- and divalent cations occupy a total of four crystallographically independent positions located in voids between the tetrahedra. Three of these sites are exclusively occupied by calcium. The fourth site is occupied by 54(1)% K and 46%(1) Na, respectively. Alternatively, the structure can be described as a heteropolyhedral framework based on corner-sharing silicate tetrahedra and [CaO6]-octahedra. The network can build up from kröhnkite-like [Ca(SiO4)2O2]-chains running along [001]. A detailed comparison with other A2B6Si4O15-compounds including topological and group-theoretical aspects is presented.
Enricofrancoite (IMA 2023-002), ideally KNaCaSi4O10, is a new litidionite-group member found as the product of high-temperature alteration of hosting silicates with the enrichment by Cu-bearing fluids at the rock-fumaroles interface related to the 1872 eruption of Somma-Vesuvius volcano, southern Italy. It occurs as euhedral and platy crystals or crusts together with litidionite, tridymite, wollastonite and Al- and Fe-bearing diopside, kamenevite, perovskite, rutile, Ti-rich magnetite and colorless Si-glass. Single crystals of enricofrancoite are transparent colorless or light blue with a vitreous lustre. Mohs hardness is 5.5. Dmeas is 2.63(3) g/cm3 and Dcalc is 2.63 g/cm3. The mineral is optically biaxial (−), α = 1.542(5), β = 1.567(5),γ = 1.575(5); 2V(meas) = 60(2)° and 2Vcalc = 58°. The mean chemical composition (wt.%, electron-microprobe data) is: SiO2 64.81, Al2O3 0.03, TiO2 0.08, FeO 0.07, MgO 1.71, CaO 10.64, CuO 2.22, Na2O 8.56, K2O 11.41, total 99.94. The empirical formula based on 10 O apfu is: K0.90Na1.03(Ca0.71Mg0.16Cu0.10)Σ=0.97Si4.02O10. The Raman spectrum contains bands at 133, 248, 265, 290, 335, 400, 438, 510, 600, 690, 1120 cm–1 and the wavenumbers of the IR absorption bands are: 424, 470, 492, 530, 600, 630, 690, 750, 788, 970, 1040, 1160 cm–1. The eight strongest lines of the powder X-ray diffraction pattern are (I-d(Å)-hkl): 42-6.75-01-1, 20-3.65-11-2, 100-3.370-02-2, 52-3.210-102, 18-3.051-111, 25-3.033-2-1-2, 22-2.834-02-3, 72-2.411-03-2. Enricofrancoite is triclinic, space group P-1, unit-cell parameters refined from the single-crystal data are a = 7.0155(4) Å, b = 8.0721(4) Å, c = 10.0275(4) Å, α = 104.420(4)°, β = 99.764(4)°, γ = 115.126(5)°, V = 472.74(5) Å3. The crystal structure has been refined from single-crystal X-ray diffraction data to R1 = 0.035 on the basis of 2078 independent reflections with Fo > 4sigma(Fo). Enricofrancoite is an H2O-free analogue of calcinaksite with 5-coordinated Ca2+ at the M site.
The modular approach is a powerful tool in current inorganic crystal chemistry. It enables not only a more detailed analysis of the known structures and the determination of structural relationships between them, but also the prediction of potentially novel structures that can be applied in modern materials science. A large number of examples of compounds with modular structures allows us to state that structural modularity is a widely spread phenomenon among natural and synthetic compounds. The use of the formalism of OD theory makes it possible to analyze the symmetry of polytypes with different crystal structures. In this review, we collected new data published in the last 15 years about OD structures and phenomena of polytypism and modularity in inorganic compounds, as well as the topological approach to the analysis of crystal structures.
The manaksite mineral KNaMnSi4O10 was synthesized and used to fabricate electrodes, which were investigated for electrochemical energy storage (EES) application using cyclic voltammetry (CV), galvanostatic charge and discharge (GCD), and electrochemical impedance spectroscopy (EIS). Optimum weight percentages (wt%) of electrode components were established as 10 wt% polytetrafluoroethylene (PTFE) binder, 15 wt% RuO2 and 5 wt% carbon black. RuO2 was added to improve electrical conductivity. A ratio of 13 : 3 for KNaMnSi4O10 : RuO2 was used in the fabrication of the electrode. A study of the suitable electrolyte and corresponding concentration to use was done using NaOH and KOH, both at concentrations of 1 M, 3 M and 6 M, with 3 M NaOH as the optimum electrolyte and concentration. The KNaMnSi4O10 yielded a specific capacity of 106 mA h g⁻¹. An investigation into the energy storage mechanism from a plot of log I(ν) vs. log ν, where I is current and ν is the scan rate gave a b value parameter of 0.8; that is, in-between 0.5 obtained for a pure battery material and 1.0 for a pure capacitor material. Accordingly, KNaMnSi4O10 exhibited a battery-supercapacitor duality phenomenon consistent with supercapattery materials. The KNaMnSi4O10 electrochemical system involved both capacitive and diffusion-controlled processes and was found to have good cyclic stability. It is concluded that KNaMnSi4O10 is a potential electrochemical energy storage material.
Gismondine-Sr, recently discovered in the Hatrurim Complex in Israel, has been recognised in a xenolith sample from the Bellerberg volcano in Germany. The empirical crystal-chemical formula indicates elevated K content: (Sr 1.74 Ca 1.05 Ba 0.09 K 1.56 Na 0.49 ) Σ4.93 [Al 7.98 Si 8.06 O 32 ]⋅9.62H 2 O. Additionally, Ba-rich gismondine and amicite have been found in the low-temperature mineral association of the pyrometamorphic rock from the Hatrurim Complex. The Raman spectra of the studied zeolites and the crystal structure of gismondine-Sr from the second occurrence are presented. A review of zeolites with GIS framework-type structure leads to the following conclusions: (1) garronite-Na and gobbinsite are equivalent and constitute a solid solution with garronite-Ca; (2) gismondine-Ca, -Sr, and amicite belong to one mineral series; (3) two zeolites series with different R -factors (defined as Si/(Si+Al+Fe)) can be distinguished within GIS topology: the garronite series ( R > 0.6) including garronite-Ca and gobbinsite, with general formula (M y D 0.5( x – y ) )[Al x Si (16– x ) O 32 ]⋅ n H 2 O, where M and D refer to monovalent and divalent cations, respectively; and the gismondine series, including amicite, gismondine-Sr and gismondine-Ca, with R ≈ 0.5, and the general formula (M y D 0.5(8– y ) )[Al 8 Si 8 O 32 ]⋅ n H 2 O. The Raman band between 475 cm –1 and 485 cm –1 is distinctive for the garronite series, whereas the band around 460 cm –1 is characteristic of the gismondine series. On the basis of these findings, a revision of GIS zeolites nomenclature is suggested.
Agrellite, NaCa2Si4O10F, is a tubular silicate mineral which crystal structure is characterized by extended [Si8O20]8– tubes and has a two-dimensional channel system. The mineral is a representative of a complex silicate family which contains some structural voids but cannot be considered as microporous because of small channel widths. However, the channel system of such minerals is able to host single guest atoms, molecules or radicals which can affect their physical properties. Presently, the exact mechanism of such hosting is undetermined. However, such information could be quite useful for materials’ application as zeolites as well as for a better understanding of their formation mechanisms. In this work we couple X-ray diffraction, infrared (IR) spectroscopy and ab initio calculations to identify structural features in agrellite from Malyy Murun massif (Russia) caused by incorporation of either H2O or OH− into the channel system. We construct structural models of water-containing NaCa2Si4O10F and identified H2O positions. The derivation of H2O sites is based on simulation of IR-spectra. Infrared spectroscopy in combination with the ab initio calculation has proven to be an effective tool for the identification of the structural positions of hydroxyl anions (OH−) and neutral water groups (H2O) in minerals.
A structure hierarchy is developed for chain-, ribbon-and tube-silicate based on the connectedness of one-dimensional polymer-isations of (TO 4) n− tetrahedra, where T = Si 4+ plus P 5+ , V 5+ , As 5+ , Al 3+ , Fe 3+ , B 3+ , Be 2+ , Zn 2+ and Mg 2+. Such polymerisations are described by a geometrical repeat unit (with n g tetrahedra) and a topological repeat unit (or graph) (with n t vertices). The connectivity of the tetrahedra (vertices) in the geometrical (topological) repeat units is denoted by the expression c T r (c V r) where c is the connect-ivity (degree) of the tetrahedron (vertex) and r is the number of tetrahedra (vertices) of connectivity (degree) c in the repeat unit. Thus c T r = 1 T r1 2 T r2 3 T r3 4 T r4 (c V r = 1 V r1 2 V r2 3 V r3 4 V r4) represents all possible connectivities (degrees) of tetrahedra (vertices) in the geometrical (topological) repeat units of such one-dimensional polymerisations. We may generate all possible c T r (c V r) expressions for chains (graphs) with tetrahedron (vertex) connectivities (degrees) c = 1 to 4 where r = 1 to n by sequentially increasing the values of c and r, and by ranking them accordingly. The silicate (sensu lato) units of chain-, ribbon-and tube-silicate minerals are identified and associated with the relevant c T r (c V r) symbols. Following description and association with the relevant c T r (c V r) symbols of the silicate units in all chain-, ribbon-and tube-silicate minerals, the minerals are arranged into decreasing O:T ratio from 3.0 to 2.5, an arrangement that reflects their increasing structural connectivity. Considering only the silicate component, the compositional range of the chain-, ribbon-and tube-silicate minerals strongly overlaps that of the sheet-silicate minerals. Of the chain-, ribbon-and tube-silicates and sheet silicates with the same O:T ratio, some have the same c V r symbols (vertex connectivities) but the tetrahedra link to each other in different ways and are topologically different. The abundance of chain-, ribbon-and tube-silicate minerals decreases as O:T decreases from 3.0 to 2.5 whereas the abundance of sheet-silicate minerals increases from O:T = 3.0 to 2.5 and decreases again to O:T = 2.0. Some of the chain-, ribbon-and tube-silicate minerals have more than one distinct silicate unit: (1) vino-gradovite, revdite, lintisite (punkaruaivite) and charoite have mixed chains, ribbons and/or tubes; (2) veblenite, yuksporite, miserite and okenite have clusters or sheets in addition to chains, ribbons and tubes. It is apparent that some chain-ribbon-tube topologies are favoured over others as of the ∼450 inosilicate minerals, ∼375 correspond to only four topologically unique graphs, the other ∼75 minerals correspond to ∼46 topologically unique graphs. Keywords: structure hierarchy, chain-silicate mineral, ribbon-silicate mineral, tube-silicate mineral, structural connectivity, stoichiometry (
This work is part of a project focused on the Somma–Vesuvius volcano and aimed at identifying Cu minerals related to mineralizing processes associated with magmatic activity in an active magmatic-hydrothermal system. A mineralogical survey was carried out on a set of samples represented by sublimates and fumarolic products from the collection of the Mineralogical Museum of the University of Naples Federico II (Italy). These samples are mainly related to most recent eruptive episodes of Vesuvius activity, from 1631 onward. Copper-bearing minerals were characterized, as well as associated minerals, by X-ray diffraction (XRD) scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS). An investigation on the structural complexity of Cu-mineral assemblages with different temperature formations was also carried out using the TOPOS software package. The main copper phases are sulfates, followed by vanadates, hydroxyhalides, oxides, carbonates, silicates and finally, phosphates. New mineral occurrences for Vesuvius, both Cu-bearing and Cu-free, are described. Nevertheless, the fumarolic/alteration minerals at Vesuvius cannot be considered of economic relevance as a copper reservoir, this type of mineralizations are significant for copper crystal chemistry and for the knowledge of the mineralogical variants. The obtained datasets can be of interest for the knowledge of volcanic byproducts of copper ore deposits (i.e., porphyry copper systems) and of (base) metal segregation processes.
