none 10.1180/minmag.2012.076.4.01 Mineralogical Society The Mineralogical Society 7149 56977549 5840 2021020408545317858 10.1180 2021-02-04T09:38:07Z 2012-08-08T12:33:23Z 2 Mineralogical Magazine Mineral. mag. 0026-461X 1471-8022 08 2012 76 4 F. Cámara F. Nestola L. Bindi A. Guastoni F. Zorzi L. Peruzzo D. Pedron Abstract Tazzoliite, ideally Ba 2 CaSr 0.5 Na 0.5 Ti 2 Nb 3 SiO 17 [PO 2 (OH) 2 ] 0.5 , is a new mineral (IMA 2011-018) from Monte delle Basse, Euganei Hills, Galzignano Terme, Padova, Italy. It occurs as lamellar pale orange crystals, which are typically a few m m thick and up to 0.4 mm long, closely associated with a diopsidic pyroxene and titanite. Tazzoliite is transparent. It has a white streak, a pearly lustre, is not fluorescent and has a hardness of 6 (Mohs' scale). The tenacity is brittle and the crystals have a perfect cleavage along {010}. The calculated density is 4.517 g cm –3 . Tazzoliite is biaxial (–) with 2V meas of ~50º, it is not pleochroic and the average refractive index is 2.04. No twinning was observed. Electronmicroprobe analyses gave the following chemical formula: (Ba 1.93 Ca 1.20 Sr 0.52 Na 0.25 Fe 0.10 2+ ) Σ4 (Nb 2.88 Ti 2.05 Ta 0.07 Zr 0.01 V 0.01 5+ ) Σ5.02 SiO 17 [(P 0.13 Si 0.12 S 0.07 ) Σ0.32 O 0.66 (OH) 0.66 ][F 0.09 (OH) 0.23 ] Σ0.32 . Tazzoliite is orthorhombic, space group Fmmm , with unit-cell parameters a = 7.4116(3), b = 20.0632(8), c = 21.4402(8) Å, V = 3188.2(2) Å3 and Z = 8. The crystal structure, obtained from single-crystal X-ray diffraction data, was refined to R 1 ( F 2 ) = 0.063. It consists of a framework of Nb(Ti) octahedra and BaO 7 polyhedra sharing apexes or edges, and Si tetrahedra sharing apexes with Nb(Ti) octahedra and BaO 7 polyhedra. The structure, which is related to the pyrochlore structure, contains three Nb(Ti) octahedra: two are Nb dominant and one is Ti dominant. Chains of A 2O 8 polyhedra [ A 2 being occupied by Sr(Ca, Fe)] extend along [100] and are surrounded by Nb octahedra. Channels formed by six Nb(Ti) octahedra and two tetrahedra, or four A 1O 8 (OH) polyhedra ( A 1 being occupied by Ba), alternate along [100]. The channels are partially occupied by [PO 2 (OH) 2 ] in two possible mutually exclusive positions, alternating with fully occupied A 3O 7 polyhedral pairs [ A 3 being occupied by Ca(Na)]. The seven strongest X-ray powder diffraction lines [ d in Å ( I / I 0) ( hkl )] are: 3.66 (60) (044), 3.16 (30) (153), 3.05 (100) (204), 2.98 (25) (240), 2.84 (50) (064), 1.85 (25) (400) and 1.82 (25) (268). Raman spectra of tazzoliite were collected in the range 150–3700 cm –1 and confirm the presence of OH groups. Tazzoliite is named in honour of Vittorio Tazzoli in recognition of his contributions to the fields of mineralogy and crystallography. 07 05 2018 08 2012 827 838 S0026461X00003662 https://www.cambridge.org/core/terms 10.1180/minmag.2012.076.4.01 https://www.cambridge.org/core/product/identifier/S0026461X00003662/type/journal_article https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0026461X00003662 http://www.ingentaconnect.com/content/minsoc/mag/2012/00000076/00000004/art00002 http://minmag.geoscienceworld.org/cgi/doi/10.1180/minmag.2012.076.4.01 Atti e Memorie dell Accademia Patavina di Scienze, Lettere ed Arti La costituzione geologia dei Colli Euganei 51 11 1935 Dal Piaz Doklady Akadamii NaukSSSR Crystal structure of girvasite 331 1372 1990 Sokolova 10.1016/j.jssc.2006.12.024 New Data on Minerals New data on komarovite series minerals 39 5 2004 Pekov SHELX. Acta Crystallographica 112 2008 Sheldrick 10.1016/j.jssc.2005.11.031 The Canadian Mineralogist The structural chemistry of kalipyrochlore, a “hydropyr-ochlore” 32 417 1994 Ercit La geologia dei Colli Euganei. 2003 Astolfi 10.1127/ejm/6/4/0503 Neues Jahrbuch fir Mineralogie, Geologie und Paldontologie Kalksilikatgesteine bei Galzignano in den Euganeen 71 342 1936 Stark 10.2113/gscanmin.40.5.1421 10.1107/S0021889807029238 The Canadian Mineralogist The Gladstone—Dale relationship—part I: derivation of new constants 14 498 1976 Mandarino 10.1127/0028-3649/2002/2002-0497 10.1093/acprof:oso/9780199545698.001.0001 10.1107/S0567739476001551 10.1524/zkri.1970.131.1-6.278 10.1021/jp0018807 American Mineralogist Interactive software for calculating and displaying X-ray or neutron powder diffract-ometer patterns of crystalline materials 78 1104 1993 Downs 10.1366/0003702854248971 10.3749/canmin.48.3.673