Skip to main content Accessibility help
×
Home

Tazzoliite: a new mineral with a pyrochlore-related structure from the Euganei Hills, Padova, Italy

  • F. Cámara (a1), F. Nestola (a2), L. Bindi (a3), A. Guastoni (a4), F. Zorzi (a2), L. Peruzzo (a5) and D. Pedron (a6)...

Abstract

Tazzoliite, ideally Ba2CaSr0.5Na0.5Ti2Nb3SiO17[PO2(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 2Vmeas 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: (Ba1.93Ca1.20Sr0.52Na0.25Fe0.10 2+)Σ4 (Nb2.88Ti2.05Ta0.07Zr0.01V0.01 5+)Σ5.02SiO17[(P0.13Si0.12S0.07)Σ0.32O0.66(OH)0.66][F0.09(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 BaO7 polyhedra sharing apexes or edges, and Si tetrahedra sharing apexes with Nb(Ti) octahedra and BaO7 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 A2O8 polyhedra [A2 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 A1O8(OH) polyhedra (A1 being occupied by Ba), alternate along [100]. The channels are partially occupied by [PO2(OH)2] in two possible mutually exclusive positions, alternating with fully occupied A3O7 polyhedral pairs [A3 being occupied by Ca(Na)]. The seven strongest X-ray powder diffraction lines [d in Å (I/I0) (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.

Copyright

Corresponding author

References

Hide All
Atencio, D., Andrade, M.B., Christy, A.G., Giere, R. and Kartashov, P.M. (2010) The pyrochlore supergroup of minerals: nomenclature. The Canadian Mineralogist, 48, 673698.
Astolfi, F. and Colombara, F. (2003) La geologia dei Colli Euganei. Edizioni Canova. Treviso.
Balic Zunic, T., Petersen, O.V., Bernhardt, H.-J. and Michelssen, H.I. (2002) The crystal structure and mineralogical description of a Na-dominant komaro-vite from the Ilimaussaq alkaline complex. South Greenland. Neues Jahrbuch fiir Mineralogie, Monatshefte, 2002, 497514.
Becker, W.J. and Will, G. (1970) Rontgen-und Neutronenbeugungsuntersuchungen an Y2Ti2O7 . Zeitschrift fir Kristallographie, 131, 278288.
Bindi, L., Petficek, V., Withers, R.L., Zoppi, M. and Bonazzi, P. (2006) Novel high-temperature com-mensurate superstructure in natural bariopyrochlore: a structural study by means of a multiphase crystal structure refinement. Journal of Solid State Chemistry, 179, 716725.
Dal Piaz, G. (1935) La costituzione geologia dei Colli Euganei. Atti e Memorie dell Accademia Patavina di Scienze, Lettere ed Arti, 51, 1119.
Downs, R.T., Bartelmehs, K.L., Gibbs, GV. and Boisen, M.B. Jr (1993) Interactive software for calculating and displaying X-ray or neutron powder diffract-ometer patterns of crystalline materials. American Mineralogist, 78, 11041107.
Dutta, P.K. and Shieh, D.C. (1985) Raman spectral study of the composition of basic silicate solutions. Applied Spectroscopy, 39, 343346.
Ercit, T.S., Hawthorne, F.C. and Cerny, P. (1994) The structural chemistry of kalipyrochlore, a “hydropyr-ochlore”. The Canadian Mineralogist, 32, 417420.
Ferraris, G., Mackovicky, E. and Merlino, S. (2008) Crystallography of Modular Materials. Oxford University Press, Oxford, UK.
Koleva, V. and Effenberger, H. (2007) Crystal chemistry of M[PO2(OH)2)]-2H2O compounds (M = Mg, Mn, Fe, Co, Ni, Zn, Cd): structural investigation of the Ni, Zn and Cd salts. Journal of Solid State Chemistry, 180, 956967
Mandarino, J.A. (1976) The Gladstone—Dale relationship—part I: derivation of new constants. The Canadian Mineralogist, 14, 498502.
Palatinus, L. and Chapuis, G (2007) Superflip— a computer program for the solution of crystal structures by charge flipping in arbitrary dimensions. Journal of Applied Crystallography, 40, 786790.
Pekov, I.V., Azarova, Y.V. and Chukanov, N. (2004) New data on komarovite series minerals. New Data on Minerals, 39, 513.
Rastsvetayeva, R.K., Tamezyan, R.A., Puscharovsky, D.Yu. and Nadeshina, T.M. (1994) Crystal structure and micro-twinning of K-rich nenadkevichite. European Journal of Mineralogy, 6, 503509.
Shannon, R.D. (1976) Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Crystallographica, A32, 751767.
Sheldrick, GM. (2008) A short history of SHELX. Acta Crystallographica, A64, 112122.
Sokolova, Y.V. and Yegorov-Tismenko, Y.K. (1990) Crystal structure of girvasite. Doklady Akadamii NaukSSSR, 331, 13721376.
Sokolova, E., Hawthorne, F.C. and Khomyakov, A.P. (2002) The crystal chemistry of fersmanite, Ca4(Na,Ca)4(Ti,Nb)4(Si2O7)2O8F3 . The Canadian Mineralogist, 40, 14211428.
Stark, M. (1936) Kalksilikatgesteine bei Galzignano in den Euganeen. Neues Jahrbuch fir Mineralogie, Geologie und Paldontologie, 71, 342361.
Su, Y., Lou Balmer, M. and Bunker, B.C. (2000) Raman spectroscopic studies of silicotitanates. Journal of Physical Chemistry B, 104, 81608169.

Keywords

Type Description Title
UNKNOWN
Supplementary materials

Cámara et al. supplementary material
Cámara tazzoliite CIF

 Unknown (29 KB)
29 KB

Tazzoliite: a new mineral with a pyrochlore-related structure from the Euganei Hills, Padova, Italy

  • F. Cámara (a1), F. Nestola (a2), L. Bindi (a3), A. Guastoni (a4), F. Zorzi (a2), L. Peruzzo (a5) and D. Pedron (a6)...

Metrics

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed