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Cavallo A. - One of the best experts on this subject based on the ideXlab platform.
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Capranicaite, (K,square)(Ca,Na)Al(4)B(4)Si(2)O(18): a new Inosilicate from Capranica, Italy, with a peculiar topology of the periodic single chain [Si(2)O(6)]
2011Co-Authors: Callegari A. M., Boiocchi M., Bellatreccia F., Caprilli E., Medenbach O., Cavallo A.Abstract:Capranicaite, ideally (K,square)(Ca,Na)Al(4)B(4)Si(2)O(18), is a new Inosilicate mineral from the Vico volcanic complex collected at Capranica, Viterbo Province, Latium, Italy. It occurs in miarolitic cavities of a feldspathoid-bearing syenite ejectum and formed by late-stage metasomatic processes related to the activity of the Vico volcano
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Capranicaite, (K,square)(Ca,Na)Al(4)B(4)Si(2)O(18): a new Inosilicate from Capranica, Italy, with a peculiar topology of the periodic single chain [Si(2)O(6)]
'Mineralogical Society', 2011Co-Authors: Callegari A. M., Boiocchi M., Bellatreccia F., Caprilli E., Medenbach O., Cavallo A.Abstract:Capranicaite, ideally (K,square)(Ca,Na)Al(4)B(4)Si(2)O(18), is a new Inosilicate mineral from the Vico volcanic complex collected at Capranica, Viterbo Province, Latium, Italy. It occurs in miarolitic cavities of a feldspathoid-bearing syenite ejectum and formed by late-stage metasomatic processes related to the activity of the Vico volcano.Published33-432.3. TTC - Laboratori di chimica e fisica delle rocceJCR Journalrestricte
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Capranicaite , (K,vac)(Ca,Na)Al4B4Si2O18:a new Inosilicate from Capranica, Italy, with a peculiar topology of the periodic single chain [Si2O6]
2011Co-Authors: Callegari A.m., Boiocchi M., Bellatreccia F., Caprilli E., Medenbach O., Cavallo A.Abstract:Capranicaite, ideally KCaNaAl4B4Si2O18, is a new Inosilicate mineral from the Vico volcanic complex collected at Capranica, Viterbo Province, Latium, Italy. It occurs in miarolitic cavities of a feldspathoid-bearing syenite ejectum and formed by late-stage metasomatic processes related to the activity of the Vico volcano.Capranicaite is monoclinic P21/n, with a = 4.8507(2), b = 16.6156(6), c = 20.5445(7) Å, β = 90.245(1)°, V = 1655.82(17) Å3, Z = 4
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Capranicaite: a new mineral from Capranica, Viterbo, Italy
2010Co-Authors: Callegari A.m., Boiocchi M., Bellatreccia F., Caprilli E., Medenbach O., Cavallo A.Abstract:Capranicaite, ideally KCaNaAl4B4Si2O18, is a new mineral recently approved by the IMA CNMNC (case no. 2009-086) found in the Vico volcanic complex at Capranica, Viterbo, Italy. Capranicaite occurs in miarolitic cavities of a feldspathoid-bearing syenite ejectum probably formed during late-stage metasomatic processes related to volcanic activity. Capranicaite forms small, tabular crystals no longer than 0.1 mm. Crystals are colourless, with a white streak and a vitreous lustre; they are not fluorescent and have a good {001} cleavage. Capranicaite is biaxial (-) with α = 1.495(1), β = 1.543(1), γ = 1.544(1); 2V(obs) = 7.3(2)°. Capranicaite is monoclinic, space group P21/n, a = 4.8507(2), b = 16.6156(6), c = 20.5445(7) Å, β = 90.245(1)°, V = 1655.82(17) Å3, Z = 4. Electron microprobe analysis gives: SiO2 20.70, Al2O3 32.91, B2O3 22.90, K2O 5.36, CaO 11.04, Na2O 4.08, Cs2O 2.20, sum 99.19%. Calculated density is 2.41 gcm-3. The formula unit, calculated on the basis of 18 O, is (K0.69Cs0.10)Ʃ0.79(Ca1.19Na0.80)Ʃ1.99Al3.91B3.99Si2.09O18. Capranicaite is a Cs bearing Inosilicate with a new topological arrangement of the 2-periodic Si2O6 single chains. The crystal structure of capranicaite consists of three overlapping layers of polyhedra (A, B, and C) normal to c. The A-layer contains the Si2O6 chains that extend along a. Respect than pyroxene, in capranicaite the Si-tetrahedra are rotated and the Si2O6 groups do not have two apical oxygens pointing towards the same direction. The B-layer is built by isolated AlO4 tetrahedra and BO3 triangles connected to form a continuous sheet of six-fold rings (3Al + 3B). Two B-layers are connected to a single sandwiched A-layer to forms a bi-dimensional B-A-B network. The B-A-B networks contain seven fold cavities not completely populated by K and minor Cs. Adjacent B-A-B bi-dimensional networks are linked together via the C-layer, constituted by isolated octahedra with a mixed (Ca,Na) population. Along c the sequence of layer results C-B-A-B-C-B-A-B-C
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Capranicaite: a new mineral from Capranica, Viterbo, Italy
2010Co-Authors: Boiocchi M., Bellatreccia F., Caprilli E., Medenbach O., Cavallo A.Abstract:recently approved by the IMA-CNMNC (no. 2009-086), found in the Vico volcanic complex at Capranica, Viterbo, Italy. Capranicaite occurs in miarolitic cavities of a feldspathoidbearing syenite ejectum, probably formed during late-stage metasomatic processes related to volcanic activity. Capranicaite forms small, tabular crystals no longer than 0.1 mm. Crystals are colourless, with a white streak and a vitreous lustre; they are not fluorescent and have a good {001} cleavage. Capranicaite is biaxial (-) with α = 1.495(1), β = 1.543(1), γ = 1.544(1); 2V(obs) = 7.3(2)°. Capranicaite is monoclinic, space group P21/n, a = 4.8507(2), b = 16.6156(6), c = 20.5445(7) Å, β = 90.245(1)°, V = 1655.82(17) Å3, Z = 4. Electron microprobe analysis gives: SiO2 20.70, Al2O3 32.91, B2O3 22.90, K2O 5.36, CaO 11.04, Na2O 4.08, Cs2O 2.20, sum 99.19%. Calculated density is 2.41 g cm-3. The formula unit, calculated on the basis of 18 O, is (K0.69Cs0.10)Ʃ0.79(Ca1.19Na0.80)Ʃ1.99Al3.91B3.99Si2.09O18. Capranicaite is a Cs bearing Inosilicate with a new topological arrangement of the 2-periodic Si2O6 single chains. The crystal structure of capranicaite consists of three overlapping layers of polyhedra (A, B, and C) normal to c. The A-layer contains the Si2O6 chains that extend along a. Respect than pyroxene, in capranicaite the Si-tetrahedra are rotated and the Si2O6 groups do not have two apical oxygens pointing towards the same direction. The B-layer is built by isolated AlO4 tetrahedra and BO3 triangles connected to form a continuous sheet of six-fold rings (3Al + 3B). Two B-layers are connected to a single sandwiched A-layer to forms a bidimensional B-A-B network. The B-A-B networks contain seven fold cavities not completely populated by K and minor Cs. Adjacent B-A-B bi-dimensional networks are linked together via the C-layer, constituted by isolated octahedra with a mixed (Ca,Na) population. Along c the sequence of layer results C-B-A-B-C-B-A-B-C (Fig. 1). The name is for the locality, Capranica, Latium, Italy, where the holotype was found
Eugeny G. Sidorov - One of the best experts on this subject based on the ideXlab platform.
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Unusual silicate mineralization in fumarolic sublimates of the Tolbachik volcano, Kamchatka, Russia – Part 1: Neso-, cyclo-, ino- and phyllosilicates
European Journal of Mineralogy, 2020Co-Authors: Nadezhda V. Shchipalkina, Igor V. Pekov, Natalia N. Koshlyakova, Sergey N. Britvin, Natalia V. Zubkova, Dmitry A. Varlamov, Eugeny G. SidorovAbstract:Abstract. This is the initial paper in a pair of articles devoted to silicate minerals from fumaroles of the Tolbachik volcano (Kamchatka, Russia). These papers contain the first systematic data on silicate mineralization of fumarolic genesis. In this article nesosilicates (forsterite, andradite and titanite), cyclosilicate (a Cu,Zn-rich analogue of roedderite), Inosilicates (enstatite, clinoenstatite, diopside, aegirine, aegirine-augite, esseneite, “Cu,Mg-pyroxene”, wollastonite, potassic-fluoro-magnesio-arfvedsonite, potassic-fluoro-richterite and litidionite) and phyllosilicates (fluorophlogopite, yanzhuminite, “fluoreastonite” and the Sn analogue of dalyite) are characterized with a focus on chemistry, crystal-chemical features and occurrence. Unusual As5+ -rich varieties of forsterite, andradite, titanite, pyroxenes, amphiboles and mica are described. General data on silicate-bearing active fumaroles and the diversity and distribution of silicates in fumarole deposits are reported. Evidence for the fumarolic origin of silicate mineralization is discussed.
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Unusual silicate mineralization in fumarolic sublimates of the Tolbachik volcano, Kamchatka, Russia – Part 2: Tectosilicates
European Journal of Mineralogy, 2020Co-Authors: Nadezhda V. Shchipalkina, Igor V. Pekov, Natalia N. Koshlyakova, Sergey N. Britvin, Natalia V. Zubkova, Dmitry A. Varlamov, Eugeny G. SidorovAbstract:Abstract. This second of two companion articles devoted to silicate mineralization in fumaroles of the Tolbachik volcano (Kamchatka, Russia) reports data on chemistry, crystal chemistry and occurrence of tectosilicates: sanidine, anorthoclase, ferrisanidine, albite, anorthite, barium feldspar, leucite, nepheline, kalsilite, sodalite and hauyne. Chemical and genetic features of fumarolic silicates are also summarized and discussed. These minerals are typically enriched with “ore” elements (As, Cu, Zn, Sn, Mo, W). Significant admixture of As5+ (up to 36 wt % As2O5 in sanidine) substituting Si is the most characteristic. Hauyne contains up to 4.2 wt % MoO3 and up to 1.7 wt % WO3 . All studied silicates are hydrogen-free, including mica and amphiboles which are F-rich. Iron-bearing minerals contain only Fe3+ due to strongly oxidizing formation conditions. In Tolbachik fumaroles, silicates were formed in the temperature range 500–800 ∘ C as a result of direct deposition from the gas phase (as volcanic sublimates) or gas–rock interactions. The zonation in distribution of major silicate minerals observed in a vertical section of the Arsenatnaya fumarole, from deep (the hottest) to upper parts is diopside + forsterite + enstatite + andradite → diopside → fluorophlogopite + diopside → sanidine + fluorophlogopite → sanidine. This is in agreement with volatilities of major species-defining metals in volcanic gases. From a crystal-chemical viewpoint, this series corresponds to the following sequence of crystallization of minerals with temperature decrease: nesosilicates → Inosilicates → phyllosilicates → tectosilicates.
A. M. Callegari - One of the best experts on this subject based on the ideXlab platform.
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capranicaite k ca na al4b4si2o18 a new Inosilicate from capranica italy with a peculiar topology of the periodic single chain si2o6
Mineralogical Magazine, 2011Co-Authors: A. M. Callegari, M. Boiocchi, F. Bellatreccia, E. Caprilli, O. Medenbach, And A CavalloAbstract:Capranicaite, ideally (K,□)(Ca,Na)Al 4 B 4 Si 2 O 18 , is a new Inosilicate mineral from the Vico volcanic complex collected at Capranica, Viterbo Province, Latium, Italy. It occurs in miarolitic cavities of a feldspathoid-bearing syenite ejectum and formed by late-stage metasomatic processes related to the activity of the Vico volcano. Capranicaite occurs as thin, tabular crystals no larger than 0.1 mm. Crystals are colourless, with a white streak and a vitreous lustre; they are brittle and their Mohs hardness is certainly 3 . Crystals are biaxial negative, non pleochroic, with α = 1.495(1), β = 1.543(1), γ = 1.544(1), 2V obs = 7.3(2)°, 2V calc = 16.0°. Capranicaite is monoclinic P 2 1 / n , with a = 4.8507(2), b = 16.6156(6), c = 20.5445(7) A, β = 90.245(1)°, V = 1655.82(17) A 3 , Z = 4. The strongest six X-ray diffraction lines in the simulated powder pattern are [ d in A ( I ) ( hkl )]: 3.234 (10) (124; 044), 4.104 (9) (21; 121), 3.424 (8) (006), 2.184 (4) (048; 64), 2.405 (4) (160), 2.425 (3) (200). EMP-WDS analysis gives: SiO 2 20.70, Al 2 O 3 32.91, B 2 O 3 22.90, K 2 O 5.36, CaO 11.04, Na 2 O 4.08, Cs 2 O 2.20, sum 99.19%; the formula, based on 18 oxygens, is: (K 0.69 Cs 0.10 ) Σ0.79 (Ca 1.19 Na 0.80 ) Σ1.99 Al 3.91 B 3.99 Si 2.09 O 18 , corresponding to the ideal formula: (K,□)(Ca,Na)Al 4 B 4 Si 2 O 18 . The crystal structure shows three overlapping layers of polyhedra parallel to (001): (1) the A layer contains periodic single chains formed by Si 2 O 6 units with a topology not previously observed; (2) the B layer contains isolated AlO 4 tetrahedra and BO 3 triangles forming a sheet of six-fold rings (3Al + 3B); (3) the C layer contains two octahedral sites: M (1) and M (2), with a mixed (Ca, Na) population. Two B layers and an intermediate A layer are vertex-connected to form a bi-dimensional B-A-B network characterized by large channels not completely populated and accommodating K and minor Cs. Along c from the origin the following layer sequence results: C-[B-A-B]-C-[B-A-B]-C.
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of the periodic single chain
2011Co-Authors: A. M. Callegari, M. Boiocchi, F. Bellatreccia, E. Caprilli, O. Medenbach, A. CavalloAbstract:a new Inosilicate from Capranica, Italy, with a peculiar topolog
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Capranicaite, (K,□)(Ca,Na)Al4B4Si2O18: a new Inosilicate from Capranica, Italy, with a peculiar topology of the periodic single chain [Si2O6]
Mineralogical Magazine, 2011Co-Authors: A. M. Callegari, M. Boiocchi, F. Bellatreccia, E. Caprilli, O. Medenbach, A. And CavalloAbstract:Capranicaite, ideally (K,□)(Ca,Na)Al 4 B 4 Si 2 O 18 , is a new Inosilicate mineral from the Vico volcanic complex collected at Capranica, Viterbo Province, Latium, Italy. It occurs in miarolitic cavities of a feldspathoid-bearing syenite ejectum and formed by late-stage metasomatic processes related to the activity of the Vico volcano. Capranicaite occurs as thin, tabular crystals no larger than 0.1 mm. Crystals are colourless, with a white streak and a vitreous lustre; they are brittle and their Mohs hardness is certainly 3 . Crystals are biaxial negative, non pleochroic, with α = 1.495(1), β = 1.543(1), γ = 1.544(1), 2V obs = 7.3(2)°, 2V calc = 16.0°. Capranicaite is monoclinic P 2 1 / n , with a = 4.8507(2), b = 16.6156(6), c = 20.5445(7) A, β = 90.245(1)°, V = 1655.82(17) A 3 , Z = 4. The strongest six X-ray diffraction lines in the simulated powder pattern are [ d in A ( I ) ( hkl )]: 3.234 (10) (124; 044), 4.104 (9) (21; 121), 3.424 (8) (006), 2.184 (4) (048; 64), 2.405 (4) (160), 2.425 (3) (200). EMP-WDS analysis gives: SiO 2 20.70, Al 2 O 3 32.91, B 2 O 3 22.90, K 2 O 5.36, CaO 11.04, Na 2 O 4.08, Cs 2 O 2.20, sum 99.19%; the formula, based on 18 oxygens, is: (K 0.69 Cs 0.10 ) Σ0.79 (Ca 1.19 Na 0.80 ) Σ1.99 Al 3.91 B 3.99 Si 2.09 O 18 , corresponding to the ideal formula: (K,□)(Ca,Na)Al 4 B 4 Si 2 O 18 . The crystal structure shows three overlapping layers of polyhedra parallel to (001): (1) the A layer contains periodic single chains formed by Si 2 O 6 units with a topology not previously observed; (2) the B layer contains isolated AlO 4 tetrahedra and BO 3 triangles forming a sheet of six-fold rings (3Al + 3B); (3) the C layer contains two octahedral sites: M (1) and M (2), with a mixed (Ca, Na) population. Two B layers and an intermediate A layer are vertex-connected to form a bi-dimensional B-A-B network characterized by large channels not completely populated and accommodating K and minor Cs. Along c from the origin the following layer sequence results: C-[B-A-B]-C-[B-A-B]-C.
Nadezhda V. Shchipalkina - One of the best experts on this subject based on the ideXlab platform.
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Unusual silicate mineralization in fumarolic sublimates of the Tolbachik volcano, Kamchatka, Russia – Part 1: Neso-, cyclo-, ino- and phyllosilicates
European Journal of Mineralogy, 2020Co-Authors: Nadezhda V. Shchipalkina, Igor V. Pekov, Natalia N. Koshlyakova, Sergey N. Britvin, Natalia V. Zubkova, Dmitry A. Varlamov, Eugeny G. SidorovAbstract:Abstract. This is the initial paper in a pair of articles devoted to silicate minerals from fumaroles of the Tolbachik volcano (Kamchatka, Russia). These papers contain the first systematic data on silicate mineralization of fumarolic genesis. In this article nesosilicates (forsterite, andradite and titanite), cyclosilicate (a Cu,Zn-rich analogue of roedderite), Inosilicates (enstatite, clinoenstatite, diopside, aegirine, aegirine-augite, esseneite, “Cu,Mg-pyroxene”, wollastonite, potassic-fluoro-magnesio-arfvedsonite, potassic-fluoro-richterite and litidionite) and phyllosilicates (fluorophlogopite, yanzhuminite, “fluoreastonite” and the Sn analogue of dalyite) are characterized with a focus on chemistry, crystal-chemical features and occurrence. Unusual As5+ -rich varieties of forsterite, andradite, titanite, pyroxenes, amphiboles and mica are described. General data on silicate-bearing active fumaroles and the diversity and distribution of silicates in fumarole deposits are reported. Evidence for the fumarolic origin of silicate mineralization is discussed.
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Unusual silicate mineralization in fumarolic sublimates of the Tolbachik volcano, Kamchatka, Russia – Part 2: Tectosilicates
European Journal of Mineralogy, 2020Co-Authors: Nadezhda V. Shchipalkina, Igor V. Pekov, Natalia N. Koshlyakova, Sergey N. Britvin, Natalia V. Zubkova, Dmitry A. Varlamov, Eugeny G. SidorovAbstract:Abstract. This second of two companion articles devoted to silicate mineralization in fumaroles of the Tolbachik volcano (Kamchatka, Russia) reports data on chemistry, crystal chemistry and occurrence of tectosilicates: sanidine, anorthoclase, ferrisanidine, albite, anorthite, barium feldspar, leucite, nepheline, kalsilite, sodalite and hauyne. Chemical and genetic features of fumarolic silicates are also summarized and discussed. These minerals are typically enriched with “ore” elements (As, Cu, Zn, Sn, Mo, W). Significant admixture of As5+ (up to 36 wt % As2O5 in sanidine) substituting Si is the most characteristic. Hauyne contains up to 4.2 wt % MoO3 and up to 1.7 wt % WO3 . All studied silicates are hydrogen-free, including mica and amphiboles which are F-rich. Iron-bearing minerals contain only Fe3+ due to strongly oxidizing formation conditions. In Tolbachik fumaroles, silicates were formed in the temperature range 500–800 ∘ C as a result of direct deposition from the gas phase (as volcanic sublimates) or gas–rock interactions. The zonation in distribution of major silicate minerals observed in a vertical section of the Arsenatnaya fumarole, from deep (the hottest) to upper parts is diopside + forsterite + enstatite + andradite → diopside → fluorophlogopite + diopside → sanidine + fluorophlogopite → sanidine. This is in agreement with volatilities of major species-defining metals in volcanic gases. From a crystal-chemical viewpoint, this series corresponds to the following sequence of crystallization of minerals with temperature decrease: nesosilicates → Inosilicates → phyllosilicates → tectosilicates.
E. Caprilli - One of the best experts on this subject based on the ideXlab platform.
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capranicaite k ca na al4b4si2o18 a new Inosilicate from capranica italy with a peculiar topology of the periodic single chain si2o6
Mineralogical Magazine, 2011Co-Authors: A. M. Callegari, M. Boiocchi, F. Bellatreccia, E. Caprilli, O. Medenbach, And A CavalloAbstract:Capranicaite, ideally (K,□)(Ca,Na)Al 4 B 4 Si 2 O 18 , is a new Inosilicate mineral from the Vico volcanic complex collected at Capranica, Viterbo Province, Latium, Italy. It occurs in miarolitic cavities of a feldspathoid-bearing syenite ejectum and formed by late-stage metasomatic processes related to the activity of the Vico volcano. Capranicaite occurs as thin, tabular crystals no larger than 0.1 mm. Crystals are colourless, with a white streak and a vitreous lustre; they are brittle and their Mohs hardness is certainly 3 . Crystals are biaxial negative, non pleochroic, with α = 1.495(1), β = 1.543(1), γ = 1.544(1), 2V obs = 7.3(2)°, 2V calc = 16.0°. Capranicaite is monoclinic P 2 1 / n , with a = 4.8507(2), b = 16.6156(6), c = 20.5445(7) A, β = 90.245(1)°, V = 1655.82(17) A 3 , Z = 4. The strongest six X-ray diffraction lines in the simulated powder pattern are [ d in A ( I ) ( hkl )]: 3.234 (10) (124; 044), 4.104 (9) (21; 121), 3.424 (8) (006), 2.184 (4) (048; 64), 2.405 (4) (160), 2.425 (3) (200). EMP-WDS analysis gives: SiO 2 20.70, Al 2 O 3 32.91, B 2 O 3 22.90, K 2 O 5.36, CaO 11.04, Na 2 O 4.08, Cs 2 O 2.20, sum 99.19%; the formula, based on 18 oxygens, is: (K 0.69 Cs 0.10 ) Σ0.79 (Ca 1.19 Na 0.80 ) Σ1.99 Al 3.91 B 3.99 Si 2.09 O 18 , corresponding to the ideal formula: (K,□)(Ca,Na)Al 4 B 4 Si 2 O 18 . The crystal structure shows three overlapping layers of polyhedra parallel to (001): (1) the A layer contains periodic single chains formed by Si 2 O 6 units with a topology not previously observed; (2) the B layer contains isolated AlO 4 tetrahedra and BO 3 triangles forming a sheet of six-fold rings (3Al + 3B); (3) the C layer contains two octahedral sites: M (1) and M (2), with a mixed (Ca, Na) population. Two B layers and an intermediate A layer are vertex-connected to form a bi-dimensional B-A-B network characterized by large channels not completely populated and accommodating K and minor Cs. Along c from the origin the following layer sequence results: C-[B-A-B]-C-[B-A-B]-C.
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of the periodic single chain
2011Co-Authors: A. M. Callegari, M. Boiocchi, F. Bellatreccia, E. Caprilli, O. Medenbach, A. CavalloAbstract:a new Inosilicate from Capranica, Italy, with a peculiar topolog
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Capranicaite, (K,□)(Ca,Na)Al4B4Si2O18: a new Inosilicate from Capranica, Italy, with a peculiar topology of the periodic single chain [Si2O6]
Mineralogical Magazine, 2011Co-Authors: A. M. Callegari, M. Boiocchi, F. Bellatreccia, E. Caprilli, O. Medenbach, A. And CavalloAbstract:Capranicaite, ideally (K,□)(Ca,Na)Al 4 B 4 Si 2 O 18 , is a new Inosilicate mineral from the Vico volcanic complex collected at Capranica, Viterbo Province, Latium, Italy. It occurs in miarolitic cavities of a feldspathoid-bearing syenite ejectum and formed by late-stage metasomatic processes related to the activity of the Vico volcano. Capranicaite occurs as thin, tabular crystals no larger than 0.1 mm. Crystals are colourless, with a white streak and a vitreous lustre; they are brittle and their Mohs hardness is certainly 3 . Crystals are biaxial negative, non pleochroic, with α = 1.495(1), β = 1.543(1), γ = 1.544(1), 2V obs = 7.3(2)°, 2V calc = 16.0°. Capranicaite is monoclinic P 2 1 / n , with a = 4.8507(2), b = 16.6156(6), c = 20.5445(7) A, β = 90.245(1)°, V = 1655.82(17) A 3 , Z = 4. The strongest six X-ray diffraction lines in the simulated powder pattern are [ d in A ( I ) ( hkl )]: 3.234 (10) (124; 044), 4.104 (9) (21; 121), 3.424 (8) (006), 2.184 (4) (048; 64), 2.405 (4) (160), 2.425 (3) (200). EMP-WDS analysis gives: SiO 2 20.70, Al 2 O 3 32.91, B 2 O 3 22.90, K 2 O 5.36, CaO 11.04, Na 2 O 4.08, Cs 2 O 2.20, sum 99.19%; the formula, based on 18 oxygens, is: (K 0.69 Cs 0.10 ) Σ0.79 (Ca 1.19 Na 0.80 ) Σ1.99 Al 3.91 B 3.99 Si 2.09 O 18 , corresponding to the ideal formula: (K,□)(Ca,Na)Al 4 B 4 Si 2 O 18 . The crystal structure shows three overlapping layers of polyhedra parallel to (001): (1) the A layer contains periodic single chains formed by Si 2 O 6 units with a topology not previously observed; (2) the B layer contains isolated AlO 4 tetrahedra and BO 3 triangles forming a sheet of six-fold rings (3Al + 3B); (3) the C layer contains two octahedral sites: M (1) and M (2), with a mixed (Ca, Na) population. Two B layers and an intermediate A layer are vertex-connected to form a bi-dimensional B-A-B network characterized by large channels not completely populated and accommodating K and minor Cs. Along c from the origin the following layer sequence results: C-[B-A-B]-C-[B-A-B]-C.