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Magnesio-hornblende from Lüderitz, Namibia: mineral description and crystal chemistry

Published online by Cambridge University Press:  16 May 2018

Roberta Oberti ,
Massimo Boiocchi ,
Frank C. Hawthorne  and
Marco E. Ciriotti
Roberta Oberti*
Affiliation:
CNR-Istituto di Geoscienze e Georisorse, Sede secondaria di Pavia, via Ferrata 1, I-27100 Pavia, Italy
Massimo Boiocchi
Affiliation:
Centro Grandi Strumenti, Università di Pavia, via Bassi 21, I-27100 Pavia, Italy
Frank C. Hawthorne
Affiliation:
Department of Geological Sciences, University of Manitoba, Winnipeg, Manitoba, R3T 2N2, Canada
Marco E. Ciriotti
Affiliation:
Associazione Micromineralogica Italiana, via San Pietro 55, I-10073 Devesi-Cirié, Italy
*
*E-mail: [email protected]
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Abstract

Magnesio-hornblende (IMA2017-059) has been characterized in a specimen collected in the sand dunes of Lüderitz, Karas Region, Namibia. The empirical formula derived from electron microprobe analysis and single-crystal structure refinement is A(□0.73Na0.22K0.05)Σ1.00B(Ca1.79Fe2+0.10Mg0.04Mn2+0.03Na0.04)Σ2.00C(Mg3.48Fe2+0.97Al0.28Fe3+0.23Cr3+0.01Ti0.03)Σ5.00T(Si7.18Al0.82)Σ8.00O22W[(OH)1.93F0.05Cl0.02]Σ2.00. Magnesio-hornblende is biaxial (–), with α = 1.640(2), β = 1.654(2), γ = 1.666(2) (measured with gel-filtered Na light, λ = 589.9 nm), 2V (meas.) = 82(1)° and 2V (calc.) = 84.9°. The unit-cell parameters are a = 9.8308(7), b = 18.0659(11), c = 5.2968(4) Å, β = 104.771(6)° and V = 909.64 (11) Å3 with Z = 2 and space group C2/m. The strongest eight reflections in the X-ray powder pattern [d values (in Å), I, (hkl)] are: 2.709, 100, (151); 8.412, 74, (110); 3.121, 73, (310); 2.541, 58, ($\bar{2}$02); 3.386, 49, (131); 2.596, 45, (061); 2.338, 41, ($\bar{3}$51); and 2.164, 39, (261).

Keywords

magnesio-hornblendeelectron-microprobe analysisoptical propertiespowder-diffraction patterncrystal-structure refinementLüderitzNamibia
Type
Article
Information
Mineralogical Magazine , Volume 82 , Issue 6 , December 2018 , pp. 1253 - 1259
Copyright
Copyright © Mineralogical Society of Great Britain and Ireland 2019 

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Footnotes

Associate Editor: Anthony Kampf

References

Bartelmehs, K.L., Bloss, F.D., Downs, R.T. and Birch, J.B. (1992) EXCALIBR II. Zeitschrift für Kristallographie, 199, 185–196.Google Scholar
Bruker, (2003) SAINT Software Reference Manual. Version 6. Bruker AXS Inc., Madison, Wisconsin, USA.Google Scholar
Cannillo, E., Germani, G. and Mazzi, F. (1983) New crystallographic software for Philips PW1100 single crystal diffractometer. CNR Centro di Studio per la Cristallografia, Internal Report 2.Google Scholar
Garzanti, E., Andò, S., Vezzoli, G., Lustrino, M., Boni, M. and Vermeesch, P. (2012) Petrology of the Namib Sand Sea: Long-distance transport and compositional variability in the wind-displaced Orange Delta. Earth-Science Reviews, 112, 173–189.Google Scholar
Hawthorne, F.C., Ungaretti, L. and Oberti, R. (1995) Site populations in minerals: terminology and presentation of results of crystal-structure refinement. Canadian Mineralogist, 33, 907–911.Google Scholar
Hawthorne, F.C., Oberti, R., Harlow, G.E., Maresch, W.V., Martin, R.F., Schumacher, J.C., and Welch, M.D. (2012) Nomenclature of the amphibole supergroup. American Mineralogist, 97, 2031–2048.Google Scholar
Mandarino, J.A. (2007) The Gladstone-Dale compatibility of minerals and its use in selecting mineral species for further studying. Canadian Mineralogist, 45, 1307–1324.Google Scholar
Oberti, R., Ungaretti, L., Cannillo, E. and Hawthorne, F.C. (1992) The behaviour of Ti in amphiboles: I. Four- and six-coordinated Ti in richterites. European Journal of Mineralogy, 4, 425–439.Google Scholar
Oberti, R., Hawthorne, F.C., Ungaretti, L. and Cannillo, E. (1995) [6]Al disorder in amphiboles from mantle peridotite. Canadian Mineralogist, 33, 867–878.Google Scholar
Oberti, R., Hawthorne, F.C., Cannillo, E. and Cámara, F. (2007) Long-range order in amphiboles. Pp. 125–172 in: Amphiboles: Crystal Chemistry, Occurrence and Health Issues (Hawthorne, F.C., Oberti, R., Della Ventura, G. and Mottana, A., editors). Reviews in Mineralogy & Geochemistry, 67. Mineralogical Society of America and the Geochemical Society, Chantilly, Virginia, USA.Google Scholar
Oberti, R., Boiocchi, M., Hawthorne, F.C., Ball, N.A. and Chiappino, L. (2016 a) Magnesio-ferri-fluoro-hornblende from Portoscuso, Sardinia, Italy: description of a newly approved member of the amphibole supergroup. Mineralogical Magazine, 80, 269–275.Google Scholar
Oberti, R., Boiocchi, M., Hawthorne, F.C., Ball, N.A., Cámara, F., Pagano, R. and Pagano, A. (2016 b) Ferro-ferri-hornblende from the Traversella Mine (Ivrea, Italy): occurrence, mineral description and crystal-chemistry. Mineralogical Magazine, 80, 1233–1242.Google Scholar
Oberti, R., Della Ventura, G., Boiocchi, M., Zanetti, A. and Hawthorne, F.C. (2017) New data on the crystal-chemistry of oxo-mangani-leakeite and mangano-mangani-ungarettiite from the Hoskins mine and their impossible solid-solution – An XRD and FTIR study. Mineralogical Magazine, 81, 707–722.Google Scholar
Robinson, K., Gibbs, G.V. and Ribbe, P.H. (1971) Quadratic elongation: a quantitative measure of distortion in coordination polyhedra. Science, 172, 567–570.Google Scholar
Shannon, R.D. (1976) Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Crystallographica, A32, 751–767.Google Scholar
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