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hellandite group

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Journal Article
Published: 01 July 2019
European Journal of Mineralogy (2019) 31 (4): 799-806.
...Roberta Oberti; Antonio Langone; Massimo Boiocchi; Ezio Bernabè; Frank C. Hawthorne The ideal formulae of two root-names of the hellandite group, i.e. mottanaite and ciprianiite, were originally given as X Ca 4 Y (CeCa) 2 Z Al T Be 2 [B 4 Si 4 O 22 ] W O 2 and X Ca 4 Y [(Th,U)REE] Σ2 Z Al T □ 2 [B...
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Journal Article
Published: 01 June 1999
American Mineralogist (1999) 84 (5-6): 913-921.
... 4 Si 4 O 22 ] tetrahedral chains of hellandite are locally cross-linked to form a sheet, which is built up by the same types of rings as in semenovite but in a different arrangement. The structure refinement and the electron- and ion-microprobe analyses provide constraints on hellandite-group...
Journal Article
Published: 01 May 2002
American Mineralogist (2002) 87 (5-6): 739-744.
...Giancarlo Della Ventura; Paola Bonazzi; Roberta Oberti; Luisa Ottolini Abstract Two new minerals of the hellandite group were found within alkali-syenitic ejecta enclosed in pyroclastic formations of the Roman Comagmatic Province (Latium, Italy). Mottanaite-(Ce) [ideally X Ca Y 4 (CeCa) Z Al T Be 2...
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Journal Article
Published: 01 May 2002
American Mineralogist (2002) 87 (5-6): 745-752.
...), together with a critical re-evaluation of the existing data on hellandite, allow a better understanding of the crystal-chemistry of the hellandite group. Relative to the crystal structure determined by Mellini and Merlino (1977) for a Y-rich sample from Predazzo (Italy), a new tetrahedrally coordinated...
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Journal Article
Published: 01 July 2006
American Mineralogist (2006) 91 (7): 1170-1177.
... synthesis from X-ray diffraction data [monoclinic, space group P 2/ a , a = 28.097(3) Å, b = 4.777(1) Å, c = 10.236(2) Å, β = 96.81(1)°, V = 1364.2(7) Å 3 , Z = 2] and was refined to a final R obs = 0.059 for 6480 F o with I o > 3σ ( I o ). The structure shows similarities with the hellandite group...
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Journal Article
Published: 01 February 1977
American Mineralogist (1977) 62 (1-2): 89-99.
...M. Mellini; S. Merlino Abstract The crystal structure determination of hellandite was made on a specimen from Predazzo, Italy ( a = 18.99, b = 4.715, c = 10.30 Å, β = 111.4°, space group P2/a ), through Patterson and Fourier methods, with data collected on a single crystal diffractometer. The least...
Journal Article
Published: 15 September 2015
The Canadian Mineralogist (2015) 53 (2): 345-356.
... of the hellandite group, which consists of borosilicate minerals having the general formula ( Oberti et al. 2002 ), X 4 Y 2 ZT 2 Si 4 B 4 O 22 W 2 or M 3 2 M 4 2 M 2 2 M 1 T 2 Si 4 B 4 O 22 (OH,F,O) 2 , where X = M 3 + M 4; M 3 = Ca 2+ , Y 3+ ; M 4 = Na + , Ca 2+ , Y 3+ , Ln 3+ (lanthanoids...
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Journal Article
Published: 01 February 2004
The Canadian Mineralogist (2004) 42 (1): 121-124.
..., Idaho, U.S.A. It occurs as irregular tufts (up to 2 mm across) of radiating acicular-to-fibrous crystals in miarolitic cavities in the granite, associated with quartz, microcline, albite, beryl, topaz, bertrandite, hellandite, zinnwaldite, fluorite, hematite and apatite. Individual crystals of potassic...
Journal Article
Published: 01 July 2002
European Journal of Mineralogy (2002) 14 (4): 809-820.
.... Sodalite occurs as well-faceted crystals inside miarolitic cavities between intersecting feldspars and it is variably altered to a kaolinite-like product. Accessory minerals include zircon, baddeleyite, stillwellite, hellandite, fluorite, apatite and monazite. Zirconolite occurs both as elongated acicular...
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Journal Article
Published: 01 February 1979
American Mineralogist (1979) 64 (1-2): 202-210.
...F. Mazzi; L. Ungaretti; A. Dal Negro; J. G. Roensbo Abstract The crystal structure of semenovite, (Fe 2+ ,Mn,Zn,Ti)RE 2 Na 0 _ 2 (Ca,Na) 8 (Si,Be) 20 (O,OH,F) 48 , Z = 2, orthorhombic, a = 13.879(5), b = 13.835(5), c = 9.942(6)A, space group Pmnn, has been determined by Patterson and Fourier...
Journal Article
Published: 01 April 1971
American Mineralogist (1971) 56 (3-4_Part_1): 395-410.
... derived by leaching of hellandite, and precipitated from warm alkaline solutions. About 60 minerals, including compounds of Y, U, Th, Nb, and Bi occur in the pegmatite; 9 of these are unidentified. Pure wakefieldite could not be obtained for chemical analysis but Y and V are important constituents. YVO 4...
Journal Article
Published: 01 October 2015
Mineralogical Magazine (2015) 79 (5): 1143-1157.
...+ and X + Y = 6 a.p.f.u., according to the crystal-chemical rules given by Oberti et al . ( 2002 ) for minerals of the hellandite group; and 13 (O,OH) p.f.u. for the epidote-supergroup minerals with H 2 O calculated by stoichiometry to 1 OH − and with the total number of cations fixed to 8 a.p.f.u...
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Journal Article
Published: 01 December 2006
The Canadian Mineralogist (2006) 44 (6): 1367-1378.
...Enrico Caprilli; Giancarlo Della Ventura; Terry C. Williams; Gian Carlo Parodi; Paola Tuccimei Abstract We here present reults of a crystal-chemical study of a suite of pyrochlore-group minerals from the holocrystalline syenitic ejecta scattered within the Plio-Pleistocene pyroclastic deposits...
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Journal Article
Published: 01 November 2005
European Journal of Mineralogy (2005) 17 (6): 847-851.
... ejected block, associated with clinopyroxene, titanite, zircon, magnetite, nepheline, a hellandite-group mineral and peprossiite-(Ce) ( Della Ventura et al. , 1993a ). The crystal-chemical formula of the studied specimen is Na 4.7 K 2.7 Ca 0.1 Si 6.1 Al 5.9 O 24 (SO 4 ) 0.8 •2H 2 O, corresponding...
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Journal Article
Published: 01 October 2009
European Journal of Mineralogy (2009) 21 (5): 1073-1080.
.... , Bonazzi , P. ( 2002 ): Re-definition, nomenclature and crystal-chemistry of the hellandite group . Am. Mineral ., 87 , 745 – 752 . Piilonen , P.C. , Lalonde , A.E. , McDonald , A.M. , Gault , R.A. , Larsen , A.O. ( 2003 ): Insights into astrophyllite-group minerals. I...
Journal Article
Published: 01 October 2009
European Journal of Mineralogy (2009) 21 (5): 1061-1071.
.... ( 1992 ): Solid solutions in mineral nomenclature . Can. Mineral ., 30 , 231 – 234 . Oberti , R. , Della Ventura , G. , Ottolini , L. , Hawthorne , F. C. , Bonazzi , P. ( 2002 ): Re-definition, nomenclature and crystal-chemistry of the hellandite group . Am. Mineral ., 87...
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Journal Article
Published: 01 August 2015
Mineralogical Magazine (2015) 79 (4): 949-963.
... – 732 [in Russian] . Efimov A.F. Dusmatov V.D. Alkhazov Yu.A. Pudovkina Z.G. Kazakova M.E. ( 1970 ) Tadzhikite – a new borosilicate of rare earths from the hellandite group . Doklady Akademii Nauk SSSR , 195 ( 5 ), 1190 – 1193 [in Russian] . Faiziev A.R...
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Journal Article
Published: 01 January 2000
European Journal of Mineralogy (2000) 12 (1): 121-127.
...Giancarlo Della VENTURA; Paolo ROSS; Gian Carlo PARODI; Annibale MOTTANA; Mati RAUDSEPP; Mauro PRENCIPE Abstract This paper relates the finding of stoppaniite, a new mineral of the beryl group, at Capranica, Vico volcanic complex, Latium, Italy. Stoppaniite occurs inside the miarolitic cavities...
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Journal Article
Published: 01 August 2006
The Canadian Mineralogist (2006) 44 (4): 943-949.
... of the pyrochlore group, yttrotantalite and yttrian fluorite. A late mineral assemblage encountered mainly in vugs and fractures comprises bertrandite, bavenite, cesian bazzite, stannian titanite, rynersonite, yttrian milarite, kainosite-(Y), hellandite-(Y), calcian hingganite-(Y), stilpnomelane, thortveitite...
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Journal Article
Published: 01 July 2016
The Canadian Mineralogist (2016) 54 (4): 879-898.
... to żabińskiite Ca(Al 0.5 Ta 0.5 )(SiO 4 )O, gadolinite-group minerals, hellandite-(Y), keiviite-(Y), pilawite-(Y), and allanite-group minerals ( Pieczka et al . 2013 , 2014 , 2015a , 2015b , 2015c ). On the basis of such a mineral assemblage, the pegmatites belong to the NYF geochemical family sensu Černý...
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