1,721,005 research outputs found
Topsøeite, FEF3(H2o)3, a new fumarolic mineral from the Hekla Volcano, Iceland
No full textThe new mineral topsøeite, FeF3(H2O)3, was found as a fumarolic product after the 1991 eruption of Hekla, Iceland. The mineral occurs as up to 20 mm large square-prismatic crystals forming occasional stepped aggregates or massive, up to 100 mm wide veins, in association with several other fluorides, hematite and opal. The experimental formula of the mineral (from scanning electron microscope energy-dispersive spectrometry data) is Fe(F2.94Cl0.04)S2.98(H2O)1.94. The deficiency of water in the formula is most probably an artefact due to experimental limitations and not a sign of dehydration. The mineral is yellow, with a calculated density of 2.330 g·cm-3, based on the ideal formula. It is tetragonal (P4/n) with a = 7.8381(3) Ǻ, c = 3.8674(1) Ǻ, V = 237.60(2) Ǻ3. The strongest eight powder diffraction lines are [d in A (relative intensity) (hkl)]: 5.55 (100) (1 1 0); 3.92 (43) (0 2 0); 3.47 (39) (0 1 1); 3.17 (22) (1 1 1); 2.77 (30) (2 2 0); 2.479 (31) (1 3 0, 3 1 0); 1.877 (16) (0 1 2), 1.753 (24) (2 4 0, 4 2 0). Rietveld refinement of the powder diffraction data confirmed the identity of topsøeite with synthetic b-FeF3(H2O)3. The crystal structure consists of straight infinite chains of [FeF4(H2O)2] octahedra extending along the c axis. The adjacent octahedra share apical F atoms, whereas the four unshared, equatorially coordinated atoms are represented by a disordered arrangement of two F and two O atoms from water molecules. Additional water molecules occupy the spaces between chains and are tetrahedrally coordinated by four (F, H2O) from four different chains binding them together via hydrogen bonds. Topsøeite is isostructural with rosenbergite, AlF3(H2O)3. Both minerals have rhombohedral polymorphs known from studies of phase systems. The polymorph of topsøeite (UM2008-27-F:AlHO), earlier supposed to be aluminium fluoride hydrate, was also found in Hekla fumaroles from the 1991 eruption, but its genetic relation with topsøeite remains unclear. Topsøeite is named after the family of Danish prominent scientists and industrialists including Haldor Topsøe the elder (1842–1935), Haldor Topsøe the younger (1913–2013) and Henrik Topsøe (1944)
Balićžunićite, Bi2O(SO4)2, a new fumarole mineral from la Fossa crater, Vulcano, Aeolian Islands, Italy
No full textBalic ́zˇunic ́ite, ideally Bi2O(SO4)2, is a new mineral found as a high-temperature fumarole sublimate
(T = 600oC) at La Fossa crater, Vulcano, Aeolian Islands, Italy. It occurs as aggregates of mm-sized
prismatic and elongated crystals (~50 mm across and up to 200 mm long) associated with anglesite,
leguernite, one other potentially new Bi-oxysulfate mineral, lillianite, galenobismutite, bismoclite,
Cd-rich sphalerite, wurtzite, pyrite and pyrrhotite. Balic ́zˇunic ́ite is colourless to white or pale brown,
transparent, non-fluorescent. It has a vitreous lustre and a white streak. Electron microprobe analyses
gives the following average chemical composition (wt.%): Bi2O3 68.68 and SO3 23.73, total 92.41. The
empirical chemical formula, calculated on the basis of 9 anions p.f.u., is Bi1.99S2O9. The calculated
density is 5.911 g/cm3.
Balic ́zˇunic ́ite is triclinic, space group P1 ̄ , with a 6.7386(3), b 11.1844(5), c 14.1754(7) A ̊ ,
a 80.082(2)o, b 88.462(2)o, g 89.517(2)o, V = 1052.01(8) A ̊ 3 and Z = 6. The six strongest reflections in
the X-ray powder-diffraction data [d in A ̊ (I) (hkl)] are: 3.146 (100) (033), 3.486 (21) (004), 3.409 (12)
(03 ̄ 1), 3.366 (7) (200), 5.562 (4) (111), 5.433 (4) (1 ̄11). Balic ́zˇunic ́ite is the natural analogue of the
stable low-temperature a form of synthetic Bi2O(SO4)2. The name is in honour of Tonci Balic ́-Zˇ unic ́
(born 1952), Professor of Mineralogy at the Natural History Museum of the University of Cophenagen.
Both the mineral and the mineral name have been approved by the IMA-CNMNC Commission
(IMA2012-098)
Provenienza di ossidiana di Selva dei Muli (Frosinone)
No full textSono stati sottoposti a determinazione di provenienza, in modo non distruttivo, gli unici tre reperti in ossidiana rinvenuti a Selva dei Muli (FR). Le analisi degli elementi maggiori mediante SEM-EDS e la determinazione delle intensità dei raggi X di alcuni elementi in traccia mediante FRX ha permesso di stabilire la fonte di approvvigionamento di due campioni di ossidiana da Lipari e di un terzo da Palmarola
Thermessaite-(NH4), (NH4)2AlF3(SO4), a new fumarole mineral from la Fossa crater at Vulcano, Aeolian Islands, Italy
Full text linkThermessaite-(NH4), ideally (NH4)2AlF3(SO4), is a new mineral found as a medium- to high-temperature (about 250-300°C) fumarole encrustation at the rim of La Fossa crater, Vulcano, Aeolian Islands, Italy. The mineral deposited as aggregates of micrometer-sized 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 colorless to white, transparent, non-fluorescent, has a vitreous luster, 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, Z = 4. The eight strongest reflections in the X-ray powder-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), 2.78 (26) (130). The average chemical composition, determined by quantitative SEM-EDS (N by difference), is (wt%): K2O 3.38, Al2O325.35, SO336.58, 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 pfu, is [(NH4)1.85K0.15]Σ2.00Al106F2.94-S0.98O3.06. The crystal structure, determined from single-crystal X-ray diffraction data [R(F) = 0.0367], is characterized by corner-sharing AlF4O2octahedra 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 SO4tetrahedra. NH4+ions occur in layers parallel to (100) which alternate regularly with (100) layers containing ribbons of corner-sharing AlF4O2octahedra 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 IMA-CNMNC commission (IMA 2011-077)
The role of the minor substitutions in the crystal structure of natural challacolloite, K2Pb2Cl5, and hephaistosite, TlPb2Cl5, from Vulcano (Aeolian Archipelago, Italy)
No full textCrystals of challacolloite, KPb(2)Cl(5), and hephaistosite, TlPb(2)Cl(5), from volcanic sublimates formed on the crater rim of the "La Fossa Crater" at Vulcano, Aeolian Archipelago, Italy, were investigated. Chemical compositions were (K(0.93)Tl(0. 02))(Sigma=0.95) Pb(2.04) (Cl(4.90)Br(0.11))(Sigma=5.01) and Tl(0.94)Pb(2.01)(Cl(4.91)Br(0.14) )(Sigma=5.05), respectively. Single crystal X-ray measurements showed monoclinic symmetry for both phases, space group P2(1)/c, with the following unit-cell parameters. a = 8.8989(4), b = 7.9717(5), c = 12.5624(8) angstrom, beta = 90.022(4)degrees, V = 891.2(1) angstrom(3), Z = 4 (challacolloite) and a = 9.0026(6), b = 7.9723(6), c = 12.5693(9) angstrom, beta = 90.046 (4)degrees, V = 902.1(1) angstrom(3), Z = 4 (hephaistosite). The structure refinements converge to R = 3.99% and R = 3.86%, respectively. The effects of Br <-> Cl and K <-> Tl substitutions on the structure of these natural compounds have been discussed
Leguernite, Bi12.67O14(SO4)5, a new Bi-oxysulfate from the fumarole deposit of “La Fossa” crater, Vulcano, Aeolian Islands, Italy.
No full textLeguernite, ideally Bi12.67O14(SO4)5, is a new mineral found in high-temperature fumarolic assemblages at La Fossa crater, Vulcano, Aeolian Islands, Italy. It occurs as aggregates of needle-shaped crystals associated strictly with anglesite, balićžunićite and an unknown Bi sulfate. Leguernite is colourless to white, transparent, non-fluorescent, has a sub-adamantine lustre and a white streak. Electron microprobe data led to the chemical formula (on the basis of 34 anions p.f.u.) (Bi12.40Pb0.15)Σ=12.55S5.08O34. The calculated density is 7.375 g cm−3. A Raman spectrum collected on a single crystal of leguernite confirmed the anhydrous nature of the mineral.
Leguernite is monoclinic, space group P2, with a = 11.2486(11), b = 5.6568(6), c = 11.9139(10) Å, β = 99.177(7)°, V = 748.39(12) Å3 and Z = 1. The crystal structure is built up of Bi–O blocks of a fluorite-like structure with Bi12O14 composition separated by a single sulfate ion along [100] and by Formula groups along [101]. It can also be described as composed of (001) layers with composition [Bi12O14(SO4)6+]n alternating with layers of composition Formula along [001]. Leguernite shows significant similarities with the synthetic Bi14O16(SO4)5 compound.
The eight strongest reflections in the powder X-ray diffraction data [d in Å (I) (hkl)] are: 3.220 (100) (013), 3.100 (95) (3İ11), 2.83 (30) (020), 2.931 (25) (302), 2.502 (25) (3İ04), 2.035 (20) (322), 1.875 (20) (3İ24) and 5.040 (15) (110).
The name is in honour of François “Fanfan” Le Guern (1942–2011), who was a very active volcanologist and specialist in volcanic gases and sublimates. Both the mineral and the mineral name have been approved by the IMA-CNMNC (2013–051)
Lucabindiite, (K,NH4)As4O6(Cl,Br), a new fumarole mineral from the “La Fossa” crater at Vulcano, Aeolian Islands, Italy
No full textLucabindiite, ideally (K,NH4)As4O6(Cl,Br), is a new mineral found as a medium-temperature fumarole encrustation (T = 170 °C) at “La Fossa” crater of Vulcano, Aeolian Islands, Italy. The mineral deposited as aggregates of micrometer-sized hexagonal and platy crystals on the surface of the pyroclastic breccia in association with arsenolite, sal ammoniac, sulfur, and amorphous arsenic-rich sulfurite. The new mineral is colorless to white, transparent, non-fluorescent, has a vitreous luster and a white streak. The calculated density is 3.68 g/cm3. Lucabindiite is hexagonal, space group P6/mmm, with a = 5.2386(7) Å, c = 9.014(2) Å, V = 214.23(7) Å3, and Z = 1. The eight strongest reflections in the X-ray powder-diffraction data [d in Å (I) (hkl)] are: 3.20 (100) (102), 2.62 (67) (110), 4.51 (52) (002), 4.54 (30) (100), 1.97 (28) (113), 1.49 (21) (115), 1.60 (21) (212), 2.26 (19) (112). Lucabindiite’s average chemical composition is (wt%): K2O 5.14, As2O3 84.71, Cl 3.63, Br 6.92, F 0.77, (NH4)2O 2.73, O=F,Cl,Br –1.84, total 102.06. The empirical chemical formula, calculated on the basis of 7 anions pfu, is [K0.51(NH4)0.49]Σ1.00 As4.00O5.93(Cl0.48Br0.40F0.19)Σ1.07. According to chemical analyses and X-ray data, lucabindiite is the natural analog of synthetic phases with general formula MAs4O6X where M = K, NH4 and × = Cl, Br, I. The crystal structure is characterized by neutral As2O3 sheets arranged parallel to (001). The As atoms of two neighboring sheets point at each other and the sheets are separated by interlayer M (=K, NH4) and × (=Cl, Br, F) atoms. The name is in honor of Luca Bindi (b. 1971), Professor of Mineralogy and former Head of the Division of Mineralogy of the Natural History Museum of the University of Florence. Both the mineral and the mineral name have been approved by the IMA-CNMNC Commission (IMA 2011-010)
Characterisation of the ionian-lucanian coastal plain aquifer (Italy)
No full textThe considered study area is, subjected to a semiarid climate, lying in Southern Italy. Data coming from 1130 boreholes have been considered to define the geological and hydrogeological set-up of the study area and for estimating the groundwater use and the salt-related groundwater quality degradation.
The aquifers are constituted by marine terraces deposits, river valley alluvial deposits and alluvial and coastal deposits. Groundwater flow is mainly unconfined in the marine terraces and in the river valleys while it becomes mostly confined in the coastal plain aquifer. Being the direct natural recharge extremely low, the recharge of this coastal aquifer is mainly guaranteed by the discharge from upward aquifers and from the river leakage.
Two dominant types of groundwater have been distinguished: the HCO3-Ca (in the marine terraces and in the alluvial deposits) and SO4-Cl-Na (in the coastal plain deposits). The variability of major ions contents is related to many factors such as the different lithologies of the aquifers, the seawater intrusion, the mixing with river water and the impact of intensive farming.
As regards the presence of the seawater intrusion in the study area, the analysis of the concentration maps of TDS, groundwater electrical conductivity and of the ions present in seawater, generally indicate that seawater contamination is relevant along a strip of land stretching for 2.5-3 km from the coastline inwards.
The new acquired knowledge permits to delineate scenarios useful for an optimization of the groundwater resources tapping and for pursuing the safeguard of them.Published225-236N/A or not JCRope
La siccità e la disponibilità di riserve idriche sotterranee nella piana di Metaponto (Basilicata)
No full textLo studio interessa la Piana di Metaponto, territorio posto nella regione Basilicata, lungo la costa ionica, costituito dalla porzione terminale dei bacini imbriferi dei fiumi Sinni, Agri, Cavone, Basento e Bradano. L’area è soggetta ad un intenso sviluppo economico connesso alle attività agricole, zootecniche e turistiche, per le quali si richiede una continua ed ingente disponibilità di acqua. Le risorse idriche sotterranee dell’area in esame sono particolarmente esposte al degrado quantitativo per la riduzione della ricarica e il sovrasfruttamento delle falde idriche sotterranee, fenomeni entrambi da ricondursi, come emerge da questo studio, alle recenti siccità. Lo studio si basa sulla caratterizzazione del complesso di relazioni esistenti tra i corpi idrici superficiali e sotterranei, in funzione delle modificazioni climatiche e antropiche del ciclo idrologico, con particolare attenzione alla disponibilità di acque sotterranee. Le più importanti modificazioni antropiche si sono succedute nel corso della seconda metà del secolo scorso. I primi decenni del ‘900 sono stati caratterizzati dallo sfruttamento moderatamente crescente delle acque sotterranee, principalmente nella parte alta della piana di Metaponto, l’unica salubre. Negli anni ’50 numerosi pozzi sono stati realizzati per soddisfare la domanda domestica ed irrigua, comparsa per l’insediamento nella piana di migliaia di coloni, reso possibile dalla bonifica e dalla riforma fondiaria. Durante gli anni ’60-’80, in seguito alla realizzazione di dighe e traverse, i pozzi precedentemente realizzati sono stati quasi del tutto sostituiti dalle reti irrigue. Infine, dagli anni ’80 ad oggi le perduranti e frequenti siccità da una parte hanno ridotto la ricarica degli acquiferi, dall’altra hanno frequentemente svuotato gli invasi e, di conseguenza, reso inefficaci gli acquedotti. Si è fatto ricorso così, sempre più spesso ed intensamente, ad integrazioni con nuovi e vecchi pozzi. La gravità del calo piezometrico non è data solo dalla riduzione della quantità di risorse idriche disponibili ma anche dal degrado qualitativo delle acque sotterranee per inquinamento salino, causato dall’intrusione marina.Published237-2446A. Monitoraggio ambientale, sicurezza e territorioope
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