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Kudryavtsevaite, Na3MgFe3+Ti4O12, a new kimberlitic mineral

Published online by Cambridge University Press:  05 July 2018

S. Anashkin ,
A. Bovkun ,
L. Bindi ,
V. Garanin  and
Y. Litvin
S. Anashkin
Affiliation:
Department of the Central Research Institute of Exploration for Non-Ferrous and Precious Metals, Varshavskoe sh. 129b, Moscow, 113545, Russia
A. Bovkun
Affiliation:
Geological Faculty, Moscow State University, Leninskie Gory, 119991, Moscow, Russia
L. Bindi*
Affiliation:
Dipartimento di Scienze della Terra, Università di Firenze, and C.N.R. – Istituto di Geoscienze e Georisorse, sezione di Firenze, Via La Pira 4, I-50121 Firenze, Italy
V. Garanin
Affiliation:
Fersman Mineralogical Museum, Leninskiy prospect 18, Moscow, 117071, Russia
Y. Litvin
Affiliation:
Institute of Experimental Mineralogy, Moscow district, 142432, Chernogolovka, Russia
*
* E-mail: [email protected]
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Abstract

Kudryavtsevaite, ideally Na3MgFe3+Ti4O12, is a new mineral from kimberlitic rocks of the Orapa area, Botswana. It occurs as rare prismatic crystals, up to 100 μm m across, associated with Mg-rich ilmenite, freudenbergite and ulvöspinel. Kudryavtsevaite is opaque with a vitreous lustre and shows a black streak. It is brittle; the Vickers hardness (VHN100) is 901 kg mm−2 (range: 876–925) (Mohs hardness ∼6). In reflected light, kudryavtsevaite is moderately bireflectant and very weakly pleochroic from dark grey to a slightly bluish grey. Under crossed polars, it is very weakly anisotropic with greyish-bluish rotation tints. Internal reflections are absent. Reflectance values (%), Rmin and Rmax, are: 21.3, 25.4 (471.1 nm), 20.6, 24.1 (548.3 nm), 20.0, 23.5 (586.6 nm) and 19.1, 22.4 (652.3 nm).

Kudryavtsevaite is orthorhombic, space group Pnma, with a = 27.714(1), b = 2.9881(3), c = 11.3564(6) Å, V = 940.5(1) Å3, and Z = 4. The crystal structure [R1 = 0.0168 for 819 reflections with I > 2σ(I)] consists of edge-sharing and corner-sharing chains composed of Mg, Fe3+ and Ti atoms coordinated by six atoms of oxygen and running along the b axis, with Na filling the tunnels formed by the chains. The eight strongest powder-diffraction lines [d in Å (I/I0) (hkl)] are: 7.17 (100) (301), 4.84 (70) (302), 2.973 (35) (901), 2.841 (50) (004), 2.706 (50) (902), 2.541 (50) (312), 2.450 (70) (611), and 2.296 (45) (612). The average results of 12 electron microprobe analyses gave (wt.%): Na2O 16.46(15), CaO 1.01(3), MgO 5.31(5), Fe2O3 22.24(32), Cr2O3 1.05(6), Al2O3 0.03(2), TiO2 53.81(50), total 99.91, corresponding to the empirical formula (Na2.89Ca0.10)Σ2.99(Ti3.67Fe1.523+Mg0.72Cr0.08)Σ5.99O12, or ideally Na3MgFe3+Ti4O12.

The new mineral has been approved by the IMA-CNMNC and named for Galina Kudryavtseva (1947–2006), a well known Russian mineralogist and founder of the Diamond Mineralogy Laboratory and scientific school for investigation of diamond mineralogy and geochemistry at the Lomonosov State University in Moscow, Russia.

Keywords

kudryavtsevaitefreudenbergitenew mineralcrystal structuremicroprobe analysiskimberlite
Type
Research Article
Information
Mineralogical Magazine , Volume 77 , Issue 3 , April 2013 , pp. 327 - 334
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2013

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