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Lobanovite, K2Na(Fe42+Mg2Na)Ti2(Si4O12)2O2(OH)4, a new mineral of the astrophyllite supergroup and its relation to magnesioastrophyllite

Published online by Cambridge University Press:  02 January 2018

Elena Sokolova ,
Fernando Cámara ,
Frank C. Hawthorne ,
Evgeny I. Semenov  and
Marco E. Ciriotti
Elena Sokolova*
Affiliation:
Department of Geological Sciences, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
Fernando Cámara
Affiliation:
Dipartimento di Scienze della Terra, Università degli Studi di Torino, via Valperga Caluso 35, I-10125 Torino, Italy
Frank C. Hawthorne
Affiliation:
Department of Geological Sciences, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
Evgeny I. Semenov
Affiliation:
Fersman Mineralogical Museum, Russian Academy of Sciences, Leninskii Prospekt, 18-2, 119071 Moscow, Russia
Marco E. Ciriotti
Affiliation:
AMI – Associazione Micromineralogica Italiana, via San Pietro 55, I-10073 Devesi-Ciriè, Italy
*
*E-mail: [email protected]
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Abstract

Lobanovite, K2Na(Fe42+Mg2Na)Ti2(Si4O12)2O2(OH)4, is a new mineral of the astrophyllite supergroup from Mt. Yukspor, the Khibiny alkaline massif, Kola Peninsula Russia. It has been known previously under the following names: monoclinic astrophyllite, magnesium astrophyllite, magnesiumastrophyllite and magnesioastrophyllite but has never been formally proposed and approved as a valid mineral species by the Commission on new Minerals, Nomenclature and Classification of the International Mineralogical Association. It has now been revalidated and named lobanovite after Dr. Konstantin V. Lobanov, a prominent Russian ore geologist who worked in the Kola Peninsula for more than forty years (Nomenclature voting proposal 15-B). Lobanovite has been described from pegmatitic cavities on Mt. Yukspor where it occurs as elongated bladed crystals, up to 0.04 mm wide and 0.2 mm long, with a straw yellow to orange colour. Associated minerals are shcherbakovite, lamprophyllite, delindeite, wadeite, umbite and kostylevite. Lobanovite is biaxial (–) with refractive indices (λ = 589 nm) α = 1.658, βcalc. = 1.687, γ = 1.710; 2Vmeas. = 81.5– 83°. Lobanovite is monoclinic, space group C2/m, a = 5.3327(2), b = 23.1535(9), c = 10.3775(4) Å, β = 99.615(1)°, V = 1263.3 (1) Å 3, Z = 2. The six strongest reflections in the powder X-ray diffraction data [d (Å), I, (hkl)] are: 3.38, 100, (003); 2.548, 90, (063); 10.1, 80, (001); 3.80, 60, (042,131); 3.079, 50, (132,062); 2.763, 90, (1̄71). The chemical composition of lobanovite was determined by electron-microprobe analysis and the empirical formula (K1.97Ba0.01)∑1.98(Na0.65Ca0.14)∑0.79 (Fe3.182+Mg2.02Na1.00Mn0.72)∑6.92(Ti1.99Nb0.06)∑2.05[(Si8.01Al0.06)∑8.07O24]O2(OH)4.03F0.19 was calculated on the basis of 30.2 (O + OH + F) anions, with H2O calculated from structure refinement, Dcalc. = 3.161 g cm–3. In the structure of lobanovite, the main structural unit is the HOH block, which consists of one close-packed O (Octahedral) and two H (Heteropolyhedral) sheets. The M(1–4) octahedra form the O sheet and the T4O12 astrophyllite ribbons and [5]-coordinated Ti-dominant D polyhedra link through common vertices to form the H sheet. The HOH blocks repeat along [001], and K and Na atoms occur at the interstitial A and B sites. The simplified and end-member formulae of lobanovite are K2Na [(Fe2+,Mn)4Mg2Na]Ti2(Si4O12)2O2(OH)4 and K2Na(Fe42+Mg2Na)Ti2(Si4O12)2O2(OH)4, respectively.

Keywords

lobanovitemagnesiumastrophylliteastrophyllite supergroupchemical compositioncrystal-structure refinement
Type
Research Article
Information
Mineralogical Magazine , Volume 81 , Issue 1 , February 2017 , pp. 175 - 181
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2017

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References

Anthony, J.W., Bideaux, R.A., Bladh, K.W. and Nichols, M.C. (1995) Handbook of Mineralogy. II Silica, Silicates. Mineral Data Publishing, Tucson, pp. 505.Google Scholar
Burke, E.A. J (2008) Tidying up mineral names: an IMA-CNMNC scheme for suffixes, hyphens and diacritical marks. MineralogicalRecord, 39, 131–135.Google Scholar
Cámara, F., Sokolova, E., Abdu, Y and Hawthorne, F.C. (2010) The crystal structures of niobophyllite, kupletskite-(Cs) and Sn rich astrophyllite; revisions to the crystal chemistry of the astrophyllite-group minerals. The Canadian Mineralogist, 48, 1–16.CrossRefGoogle Scholar
Khomyakov, A.P. (1995) Mineralogy of Hyperagpaitic Alkaline Rocks. Clarendon Press, Oxford, UK, pp. 151.Google Scholar
Mandarino, J.A. (1981) The Gladstone-Dale relationship. Part IV The compatibility concept and its application. The Canadian Mineralogist, 19, 441–450.Google Scholar
Peng, S. and Ma. Z. (1963) The discovery of a new type of an Si—O ribbon — crystal-structure analysis of astrophyllite. Scientica Sinica, 12, 272–276 [in Russian].Google Scholar
Piilonen, P.C., LaLonde, A.E., McDonald, A.M., Gault, R.A. and Larsen, A.O. (2003a) Insights into astro-phyllite-group minerals. I. Nomenclature, compos-ition and development of a standardized general formula. The Canadian Mineralogist, 41, 1–26.CrossRefGoogle Scholar
Piilonen, P.C., McDonald, A.M. and LaLonde, A.E. (2003b) Insights into astrophyllite-group minerals. II. Crystal chemistry. The Canadian Mineralogist, 41, 27–54.CrossRefGoogle Scholar
Semenov, E.I. (1959) Lithian and other micas and hydro-micas in alkaline pegmatites of Kola Peninsula. Trudy Mineralogicheskogo Muzeya, N9,107–137 [in Russian].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.CrossRefGoogle Scholar
Shi, N., Ma, Z., Li, G., Yamnova, N.A. and Pushcharovsky, D.Y (1998) Structure refinement of monoclinic astrophyllite. Acta Crystallographica, B54, 109–114.CrossRefGoogle Scholar
Sokolova, E. (2012) Further developments in the structure topology of the astrophyllite-group minerals. Mineralogical Magazine, 76, 863–882.CrossRefGoogle Scholar
Sokolova, E. and Cámara, F (2008) Re-investigation of the crystal structure of magnesium astrophyllite. European Journal of Mineralogy, 20, 253–260.CrossRefGoogle Scholar
Sokolova, E., Cámara, F., Hawthorne, F.C. andCiriotti, M. E (2017) The astrophyllite supergroup: nomenclature and classification. Mineralogical Magazine, 81, 143–150.CrossRefGoogle Scholar
X-ray Laboratory, Hubei Geologic College (1974) The crystal chemistry of astrophyllite group minerals. Scientica Sinica, 1, 18–33 [in Chinese].Google Scholar