Montetrisaite, a new hydroxy-hydrated copper sulfate species from Monte Trisa, Vicenza, Italy

Montetrisaite, a new hydroxy-hydrated copper sulfate mineral species from Monte Trisa, Torrebelvicino, Vicenza, in Italy, has chemical formula Cu6(SO4)(OH)10•2H2O. It is associated with galena, sphalerite, chalcopyrite, cerussite, anglesite, oethite, langite, posnjakite, linarite and redgillite. The crystals are blue, vitreous, transparent, striated vertically, with a cleavage, {001}. The diffraction pattern shows strong reflections pointing to an orthorhombic unit-cell with a 2.989(2), b 16.970(5), c 14.812(4) Å, space group Cmc21, Z = 2. The strongest reflections [d in Å(Irel)(hkl)] are: 7.45(100)(002), 3.73(35)(004), 2.788(18)(061), 2.503(14)(132) and 1.595(20)(175). In addition, very weak and diffuse reflections occur, which point to a monoclinic cell with a doubled a parameter. The crystal structure is built up of layers of edge-sharing Jahn–Teller-distorted Cu-centered octahedra, to which single SO4 groups are connected on one side. Between the layers, H2O molecules are located, and the layers are connected through hydrogen bonds. The refined average structure shows sulfate groups and H2O molecules in both their statistically possible positions; in the real structure, however, only one half of those positions can be really occupied. The new mineral is structurally related to posnjakite, wroewolfeite, langite, and spangolite. On the other hand, its structure is significantly different from that of redgillite Cu6(SO4)(OH)10•H2O, which has a very similar chemical formula

Tancaite-(Ce), ideally FeCe(MoO4)3•3H2O: description and average crystal structure

Tancaite-(Ce), ideally FeCe(MoO4)3•3H2O, is a new mineral occurring within cavities in the quartz veins which cut the granite at Su Seinargiu, Sarroch (CA), Sardinia, Italy. It is a secondary mineral formed in the oxidation zone of a sulfide ore vein. Associated minerals are quartz, muscovite, molybdenite, pyrite, and a mendozavilite-like phase. Tancaite-(Ce) is red or pale brown in colour, with a vitreous to adamantine lustre. Electron microprobe analyses give (wt %) SiO2 0.34, CaO 0.09, Fe2O3 11.29, SrO 0.02, La2O3 5.04, Ce2O3 10.35, Pr2O3 1.07, Nd2O3 3.66, Sm2O3 0.19, ThO2 2.58, UO2 0.17, MoO3 58.62, and H2O (calculated) 7.43, with a sum of 100.85, from which the empirical formula is calculated. The empirical formula Fe3+1.03(Ce0.46La0.23Nd0.16Pr0.05Sm0.01U0.01Th0.07)Σ = 0.99(Mo2.96Si0.04)Σ = 3.00O12•3H2O can be simplified as Fe3+(REE)(MoO4)3•3H2O and idealized as FeCe(MoO4)3•3H2O. The presence of H2O was confirmed by micro-Raman spectrometry (stretching and bending vibrations of O–H). The calculated density is 3.834 g cm−3. The X-ray diffraction pattern of tancaite-(Ce) is characterized by a set of strong reflections, which point to a cubic subcell with a = 6.870(1) Å and space group Pm3 ¯ m, plus a set of superstructure reflections. Tancaite-(Ce) displays a new structure type not previously reported in natural and synthetic molybdates. By considering only the strong reflections, it was possible to solve and refine its average structure (R1=0.038 for 192 unique reflections with I > 2σ(I)). The crystal structure consists of FeO6 octahedra centred at the origin of the cubic subcell and linked together through MoO4 tetrahedra by corner sharing. The Mo-centred tetrahedra are statistically distributed in four symmetry-related positions, with one-fourth occupancy. In the centre of the cubic unit cell the REE cations exhibit a 6+3 coordination, bonding six oxygen atoms and three H2O molecules, each of them being disorderly distributed in four symmetry-related positions. One of the possible supercells, with a 48-fold volume with respect to the primitive cubic small subcell, corresponded to a rhombohedral lattice, with a ≈ 19.43 and c ≈ 47.60 Å in the hexagonal setting. Several unsuccessful trials were performed to solve the real crystal structure of tancaite, by indexing the additional superstructure reflections and using their intensities to refine an ordered structural model. The new mineral has been approved by the IMA CNMNC (no. 2009-097). The name comes from Giuseppe Tanca, an Italian amateur mineralogist, who discovered the mineral and gave it to us for studying

Food Sauces to Understand Volcanoes: a Learning Sequence in Middle School

Some volcanic processes occur at pressures and temperatures very different from daily experience. Such extreme conditions, unreproducible in the classroom, can lead children to build concepts about volcanic phenomena very different from the reality (Greca & Moreira, 2000; Dove, 1998). The didactic goals of this learning sequence concern the relationships between the viscosity of magmas and types of erupted materials and their consequences on volcano shapes, to favour pupils’ comprehension of what a volcano is. Viscosity and its temperature dependence can be easily experimented in class with analogue materials at room temperature (Baker et al., 2004). Our research aims are to observe the development of the thought of pupils of middle schools on volcanic phenomena; this allowed to put in evidence the benefits of this approach and to give suggestions to avoid possible critical points.We have experimented a hands-on learning sequence about volcanoes in four third classes of Tuscan middle schools, for an amount of 95 pupils, 48 females and 47 males. Sharing the principles of constructivism, we think useful that pupils start from their own direct experience for understanding natural phenomena not directly observable. Therefore, we start from the experiences and knowledge of children to build a inquiry-based itinerary (Minner et al., 2010; Pieraccioni et al., 2016). The learning sequence begins with a practical activity in which we employ common and well-known materials to introduce the concept of viscosity in order to relate various kinds of magma to the shape of volcanoes. One of the benefits of this approach is to overcome the problems of introducing complex concepts such as acidity of magmas or silica content, far from the pupils’ experience and knowledge. These concepts are often used in Italian middle school textbooks to describe and classify volcanoes. The result is a list of names to learn by heart. On the contrary, by using oil, ketchup, peanut butter or honey, pupils become familiar with concepts such as viscosity, behavior of fluids, magma, lava, slope of flanks and they can begin to comprehend why volcanoes have got differently named forms

The Crystal Structure of Tobermorite 14 Å (Plombierite), a C-S-H phase

The crystal structure of tobermorite 14 Å (plombierite) was solved by means of the application of the order-disorder (OD) theory and was refined through synchrotron radiation diffraction data. Two polytypes were detected within one very small crystal from Crestmore, together with possibly disordered sequences of layers, giving diffuse streaks along c*. Only one of the two polytypes, could be refined: it has B11b space group symmetry and cell parameters a = 6.735(2) Å, b = 7.425(2) Å, c = 27.987(5) A, γ = 123.25(1)° . The refinement converged to R = 0.152 for 1291 reflections with F 0>4σ(F 0). The characteristic reflections of the other polytype, F2dd space group, a ≈11.2 Å, b ≈ 7.3 Å, c ≈ 56 Å, were recognized but they were too weak and diffuse to be used in a structure refinement. The structure of tobermorite 14 Å is built up of complex layers, formed by sheets of sevenfold coordinated calcium cations, flanked on both sides by wollastonite-like chains. The space between two complex layers contains additional calcium cations and H 2O molecules; their distribution, as well as the system of hydrogen bonds, are presented and discussed. The crystal chemical formula indicated by the structural results is Ca 5Si 6O 16(OH) 2 ·7H 2O

‘Hartite’ renamed branchite

Historical samples of branchite, described by the Tuscan naturalist Paolo Savi (1798–1871) at the end of the 1830s, were re-examined through single-crystal X-ray diffraction, showing their identity with hartite, C20H34, a hydrocarbon mineral described by Haidinger in 1841. The refined unit-cell parameters are a = 11.4116(7), b = 20.9688(12), c = 7.4100(4) Å, α = 93.947(2), β = 100.734(2), γ = 80.524(2)°, V = 1716.99(17) Å3 and Z = 4; space group P1. The crystal structure was solved and refined up to R1 = 0.0424 for 13512 reflections with Fo > 4σ(Fo) and 1265 refined parameters. As the name ‘branchite’ has priority over ‘hartite’, the reinstatement of the former name and the discreditation of the latter were approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA–CNMNC). Branchite is one of only eleven minerals formed by C and H listed in the official IMA List of Minerals. The type locality of branchite is the Botro di Lavajano, Monte Vaso, Chianni, Pisa, Tuscany, Italy. Neotype material is kept in the Natural History Museum of the Pisa University under catalogue number 14426

Crystal structure of afghanite, the eight-layer member of the cancrinite-group: Evidence for long-range Si,Al ordering

Afghanite, ideally [(Na,K)(22)Ca-10][Si24Al24O96](SO4)(6)Cl-6, is the eight-layer member of the cancrinite-group (ABABACAC stacking sequence). Its structure was refined in the P31c space group to R = 4.5% by means of single-crystal X-ray diffraction data. The cell parameters are a = 12.8013(7) Angstrom, c = 21.4119(18) Angstrom. The P6(3)mc space group proposed in a previous structure refinement is not consistent with the ordered Si,AI pattern suggested by an Si/Al ratio equal to 1 shown by afghanite and other members of the cancrinite-group. The Si-O and Al-O bond distances, 1.61(2) Angstrom and 1.72(2) Angstrom respectively, found in the structure refinement, are in accordance with an ordered Si,AI distribution which is allowed by the P31c space group, a maximal non isomorphic subgroup of P6(3)mc. Afghanite contains six 11-hedra (cancrinite) cages and two 23-hedra (liottite) cages. Four cancrinite cages are stacked along [0 0 z]. They contain a regular....Ca-Cl-Ca-Cl.... chain similar to that observed in davyne and related phases: in particular Ca is located near the center of the bases whereas Cl is near the center of the cage. A liottite cage with a base-sharing cancrinite cage is stacked along [2/3 1/3 z] and [1/3 2/3 z]. The liottite cage hosts a maximum of three sulphate groups which alternate regularly with cation-containing planes. The cancrinite cage, that shares the bases with the liottite cages, presents a disordered distribution of Cl and F reading to two possible configurations similar to those observed in liottite

The soil in the classroom: a middle school case study

The Earth sciences have a relevant role in building both scientific competences and citizenship skills; nevertheless, in Italian middle and high schools these are prevalently taught with a poorly effective transmissive approach. This work presents the results of a research carried out choosing the soil as a topic and a class of 11-12 years old pupils as target, aimed at exploring the effectiveness of laboratory-based teaching on the acquisition of permanent scientific competences and on the birth of an autonomous way of learning to learn. The teaching approach used well assessed didactic instruments such as the work group, the exercise book and the sharing of observations. The results show that most pupils were able to use the acquired scientific knowledges and skills in different situations and became more aware of their own learning.Malgré l’importance du rôle des sciences de la Terre pour construire des compétences scientifiques ainsi que citoyennes, l'école secondaire Italienne les enseigne surtout par une méthode transmissive et peu efficace. Ce travail montre les résultats d'une recherche réalisée en choisissant le sol comme sujet d’enseignement avec une classe d’élèves de 11-12 ans. Nous nous sommes demandé si un enseignement fondé sur les activités pratiques est efficace pour l'acquisition de compétences et pour la naissance d'une autonomie d’apprentissage. La méthode d'enseignement s'appuie sur des outils didactiques déjà éprouvés, comme le travail en groupe, le cahier d’exercices, la mise en commun des observations. Les résultats montrent que les élèves ont employé leurs connaissances et habiletés scientifiques dans plusieurs situations et ils ont amélioré leur autonomie dans leurs apprentissages

Thermal behaviour of Al-rich tobermorite

The tobermorite supergroup is composed by a number of calcium-silicate-hydrate (C-S-H) minerals characterized by different hydration states and sub-cell symmetries. Taking into account their basal spacing, closely related to the hydration state, phases having a 14 Å (plombierite), 11 Å (tobermorite, kenotobermorite, and clinotobermorite), and 9 Å (riversideite) basal spacing have been described. Tobermorite and kenotobermorite belong to the so-called tobermorite group and differ for their thermal behaviour which can be "normal" (the phase shrinks to a 9 Å phase at 300 °C) or "anomalous" (the phase preserves its 11 Å basal spacing at 300 °C). Specimens of Al-rich tobermorite from Montalto di Castro and Vallerano, Latium, Central Italy, showing a "normal" thermal behaviour, were studied in order to describe the transition from the 11 Å to the 9 Å phase by means of thermogravimetric-differential scanning calorimetry (TG-DSC) analyses as well as in situ and ex situ X-ray diffraction experiments. The TG-DSC analyses showed a continuous mass loss from 100 °C up to 700 °C, with different mass loss gradients between 100 °C up to 300 °C and between 300 °C up to 700 °C, corresponding to the dehydration of tobermorite and dehydroxylation of "tobermorite 9 A", respectively. Above 700 °C, "tobermorite 9 Å" is replaced by wollastonite. The X-ray powder diffraction data were collected at the GILDA beamline of the ESRF, Grenoble, France, from room temperature up to ca. 840 °C. Tobermorite is completely replaced by the 9 A phase at ca. 300 °C, whereas the latter is transformed into wollastonite at ca. 700 °C. The transition from the 11 Å to the 9 Å phase seems to be favoured by the transient appearance of a clinotobermorite-like compound

Derbylite and graeserite from the Monte Arsiccio mine (Apuan Alps, Tuscany, Italy): occurrence and crystal-chemistry

New occurrences of derbylite, Fe2+xFe3+4-2xTi4+3+xSb3+O13(OH), and graeserite, Fe2+xFe3+4-2xTi4+3+xAs3+O13(OH), have been identified in the Monte Arsiccio mine, Apuan Alps (Tuscany, Italy). Derbylite occurs as prismatic to acicular black crystals in carbonate veins.Iron and Ti are replaced by V (up to 0.29 atoms per formula unit, apfu) and minor Cr (up to0.4 apfu). Mössbauer spectroscopy confirmed the occurrence of Fe 2+ (up to 0.73 apfu), along with Fe 3+ . The Sb/(As+Sb) atomic ratio range between 0.73 and 0.82. Minor Ba and Pb (up to 0.04 apfu) occur. Derbylite is monoclinic, space group P21/m, with unit-cell parameters a 7.1690(3), b 14.3515(7), c 4.9867(2) Å, β 104.820(3)°, V 495.99(4) Å 3 . The crystal structure was refined to R1 = 0.0352 for 1955 reflections with Fo > 4σ(Fo). Graeserite occurs as prismatic to tabular black crystals, usually twinned, in carbonate veins or as as porphyroblasts in schist. Graeserite in the first kind of assemblage is V-rich (up to 0.66 apfu), whereas it is V-poor in the second one (0.03 apfu). Along with minor Cr (up to 0.06 apfu), this element replaces Fe and Ti. The occurrence of Fe 2+ (up to 0.68 apfu) is confirmed by Mössbauer spectroscopy. Arsenic is dominant over Sb and detectable amounts of Ba and Pb have been measured (up to 0.27 apfu). Graeserite is monoclinic, space group C2/m. Unit-cell parameters are a 5.0225(7), b 14.3114(18), c 7.1743(9) Å, β 104.878(3)°, V 498.39(11) Å 3 and a 5.0275(4), b 14.2668(11), c 7.1663(5) Å, β 105.123(4)°, V 496.21(7) Å3 . The crystal structures of two graeserite samples were refined to R1 = 0.0399 and 0.0237 for 428 and 1081 reflections with Fo > 4σ(Fo), respectively. Derbylite and graeserite have homeotypic relations. They share the same tunnel structure, characterized by an octahedral framework and cuboctahedral cavities, hosting (As/Sb)O3 groups and (Ba/Pb) atom

Fukalite: an example of OD structure with two-dimensional disorder

The real crystal structure of fukalite, Ca4Si2O 6(OH)2(CO3), was solved by means of the application of order-disorder (OD) theory and was refined through synchrotron radiation diffraction data from a single crystal. The examined sample came from the Gumeshevsk skarn copper porphyry deposit in the Central Urals, Russia. The selected crystal displays diffraction patterns characterized by strong reflections, which pointed to an orthorhombic sub-structure (the "family structure" in the OD terminology), and additional weaker reflections that correspond to a monoclinic real structure. The refined cell parameters are a = 7.573(3), b = 23.364(5), c = 11.544(4) Å, β = 109.15(1)°, space group P21/c. This unit cell corresponds to one of the six possible maximum degree of order (MDO) polytypes, as obtained by applying the OD procedure. The derivation of the six MDO polytypes is presented in the Appendix1. The intensity data were collected at the Elettra synchrotron facility (Trieste, Italy); the structure refinement converged to R = 0.0342 for 1848 reflections with I > 2σ(I) and 0.0352 for all 1958 data. The structure of fukalite may be described as formed by distinct structural modules: a calcium polyhedral framework, formed by tobermorite-type polyhedral layers alternating along b with tilleyitetype zigzag polyhedral layers; silicate chains with repeat every fifth tetrahedron, running along a and linked to the calcium polyhedral layers on opposite sides; and finally rows of CO3 groups parallel to (100) and stacked along a