Hostname: page-component-586b7cd67f-g8jcs Total loading time: 0 Render date: 2024-11-29T00:33:09.686Z Has data issue: false hasContentIssue false
  • English
  • Français

Heklaite, KNaSiF6, a new fumarolic mineral from Hekla volcano, Iceland

Published online by Cambridge University Press:  05 July 2018

A. Garavelli ,
T. Balić-Žunić ,
D. Mitolo ,
P. Acquafredda ,
E. Leonardsen  and
S. P. Jakobsson
A. Garavelli*
Affiliation:
Dipartimento Geomineralogico, Università di Bari, via E. Orabona 4, I–70125 Bari, Italy
T. Balić-Žunić
Affiliation:
Department of Geography and Geology, University of Copenhagen, Øster Voldgade 10, DK-1350 København K, Denmark
D. Mitolo
Affiliation:
Dipartimento Geomineralogico, Università di Bari, via E. Orabona 4, I–70125 Bari, Italy
P. Acquafredda
Affiliation:
Dipartimento Geomineralogico, Università di Bari, via E. Orabona 4, I–70125 Bari, Italy
E. Leonardsen
Affiliation:
St. Karlsmindevej 46, DK-3390 Hundested, Denmark
S. P. Jakobsson
Affiliation:
Icelandic Institute of Natural History, Hlemmur 3, P.O. Box 5320, IS-125 Reykjavik, Iceland
*
*E-mail: [email protected]
Get access Rights & Permissions [Opens in a new window]

Abstract

Heklaite, with the ideal formula KNaSiF6, was found among fumarolic encrustations collected in 1992 on the Hekla volcano, Iceland. Heklaite forms a fine-grained mass of micron- to sub-micron-sized crystals intimately associated with malladrite, hieratite and ralstonite. The mineral is colourless, transparent, non-fluorescent, has a vitreous lustre and a white streak. The calculated density is 2.69 g cm–3. An SEM-EDS quantitative chemical analysis shows the following range of concentrations (wt.%): Na 11.61–12.74 (average 11.98), K 17.02–18.97 (average 18.29), Si 13.48 –14.17 (average 13.91), F 54.88–56.19 (average 55.66). The empirical chemical formula, calculated on the basis of 9 a.p.f.u., is Na1.07K0.96Si1.01F5.97. X-ray powder diffraction indicates that heklaite is orthorhombic, space group Pnma, with the following unit-cell parameters: a = 9.3387(7) Å, b = 5.5032(4) Å, c = 9.7957(8) Å , V = 503.43(7) Å3, Z = 4. The eight strongest reflections in the powder diffraction pattern [d in Å (I/I0) (hkl)] are: 4.33 (53) (102); 4.26 (56) (111); 3.40 (49) (112); 3.37 (47) (202); 3.34 (100) (211); 2.251 (27) (303); 2.050 (52) (123); 2.016 (29) (321). On the basis of chemical analyses and X-ray data, heklaite corresponds to the synthetic compound KNaSiF6. The name is for the type locality, the Hekla volcano, Iceland.

Keywords

heklaitenew mineralsublimatesfumarolesfluorosilicatecrystal structureHeklaIceland
Type
Research Article
Information
Mineralogical Magazine , Volume 74 , Issue 1 , February 2010 , pp. 147 - 157
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2010

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Acquafredda, P. and Paglionico, A. (2004) SEM-EDS microanalyses of microphenocrysts of Mediterranean obsidians: a preliminary approach to source discrimination. European Journal of Mineralogy, 16, 419–429.CrossRefGoogle Scholar
De Hoog, J.C.M., Van Bergen, M.J. and Jacobs, M.H.G. (2005) Vapour-phase crystallisation of silica -from SiF4-bearing volcanic gases. Annals of Geophysics, 48, 775–785.Google Scholar
Fábry, J., Chval, J. and Petřiček, V. (2001) A new modification of diammonium hexafluorosilicate, (NH4)2[SiF6]. Acta Crystallographica E, 57, 90–91.CrossRefGoogle Scholar
Fischer, J. and Krämer, V. (1991) Crystal structure of KNaSiF6 . Materials Research Bulletin, 26, 925–930.CrossRefGoogle Scholar
Gossner, B. and Kraus, O. (1934) Das Kristallgitter von Ammoniumhexafluorosilikat (NH4)2SiF6 . Zeitschrift für Kristallographie, 88, 223–225.Google Scholar
Gramaccioli, C.M. and Campostrini, I. (2007) Demartinite, a new polymorph of K2SiF6 from La Fossa crater, Vulcano, Aeolian Islands, Italy. The Canadian Mineralogist, 45, 1275–1280.CrossRefGoogle Scholar
Gudmundsson, A., Oskarsson, N., Grönvold, K., Saemundsson, K., Sigurdsson, O., Stefansson, R., Gislason, S.R., Einarsson, P., Brandsdottir, B., Larsen, G., Johannesson, H. and Thordarson, Th. (1992) The 1991 eruption of Hekla, Iceland. Bulletin of Volcanology, 54, 238–246.CrossRefGoogle Scholar
Hester, J.R., Maslen, E.N. and Spadaccini, N. (1993) Accurate synchrotron radiation Dr maps for K2SiF6 and K2PdCl6 . Acta Crystallographica B, 49, 967–973.CrossRefGoogle Scholar
Jakobsson, S.P., Jonasson, K. and Sigurdsson, I.A. (2008 a) The three igneous rock series of Iceland. Jökull, 58, 117–138.Google Scholar
Jakobsson, S.P., Leonardsen, E., Balić-Žunič, T. and Jónsson, S.S. (2008 b) Encrustations from three recent volcanic eruptions in Iceland: The 1963–1967 Surtsey, the 1973 Eldfell and the 1991 Hekla eruptions. Fjölrit Náttúrufraedistofnunar, 52, 65 pp.Google Scholar
Ketelaar, J.A.A. (1935) Die Kristallstruktur von K-, Rb-, Cs- und Tl-Silicofluorid und von LiMnO4·3H2O. Zeitschrift für Kristallographie, 92, 155–156.Google Scholar
Rosenberg, P.E. (1973) HF/SiF4 ratios in volcanic and magmatic gases. Geochimica et Cosmochimica Acta, 37, 109–112.CrossRefGoogle Scholar
Ruste, J. (1979) X-ray spectrometry. Pp. 215–267 in: Microanalysis and Scanning Electron Microscopy (Maurice, F., Meny, L. and Tixier, R., editors). Les Editions de Physique, Orsay, France.Google Scholar
Schäfer, G.F. (1986) The crystal structures of Na2TiF6 and Na2SiF6 . Zeitschrift für Kristallographie, 175, 269–276.Google Scholar
White, A.F. and Hochella, M.F. Jr (1992) Surface chemistry associated with the cooling and subaerial weathering of recent basalt flows. Geochimica et Cosmochimica Acta, 56, 3711–3721.CrossRefGoogle Scholar
Zalkin, A., Forrester, J.D. and Tempelton, D.H. (1964) The crystal structure of sodium fluosilicate. Acta Crystallographica, 17, 1408–1412.CrossRefGoogle Scholar