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Kenoplumbomicrolite, (Pb,□)2Ta2O6[□,(OH),O], a new mineral from Ploskaya, Kola Peninsula, Russia

Published online by Cambridge University Press:  28 February 2018

Daniel Atencio*
Affiliation:
Instituto de Geociências, Universidade de São Paulo, Rua do Lago, 562, 05508-080, São Paulo, SP, Brazil
Marcelo B. Andrade
Affiliation:
Department of Physics and Interdisciplinary Science, São Carlos Institute of Physics, University of São Paulo, Caixa Postal 369, 13560-970, São Carlos, SP, Brazil
Luca Bindi
Affiliation:
Dipartimento di Scienze della Terra, Università di Firenze, Via G. La Pira 4, I-50121 Florence, Italy
Paola Bonazzi
Affiliation:
Dipartimento di Scienze della Terra, Università di Firenze, Via G. La Pira 4, I-50121 Florence, Italy
Matteo Zoppi
Affiliation:
Dipartimento di Scienze della Terra, Università di Firenze, Via G. La Pira 4, I-50121 Florence, Italy
Chris J. Stanley
Affiliation:
Economic and Environmental Earth Sciences Division, Earth Sciences Department, Natural History Museum, Cromwell Road, London SW7 5BD, UK
Roy Kristiansen
Affiliation:
P.O. Box 32, N–1650 Sellebakk, Norway
*

Abstract

This study presents a complete characterization of kenoplumbomicrolite, (Pb,□)2Ta2O6[□,(OH),O], occurring in an amazonite pegmatite from Ploskaya Mountain, Western Keivy Massif, Kola Peninsula, Murmanskaja Oblast, Northern Region, Russia.

Kenoplumbomicrolite occurs in yellowish brown octahedral, cuboctahedral and massive crystals, up to 20 cm, has a white streak, a greasy lustre and is translucent. The Mohs hardness is ~6. Attempts to measure density (7.310–7.832 g/cm3) were affected by the ubiquitous presence of uraninite inclusions. Reflectance values were measured in air and immersed in oil. Kenoplumbocrolite is optically isotropic. The empirical formula is (Pb1.300.30Ca0.29Na0.08U0.03)Σ2.00(Ta0.82Nb0.62Si0.23Sn4+0.15Ti0.07Fe3+0.10Al0.01)Σ2.00O6[□0.52(OH)0.25O0.23]Σ1.00 (from the crystal used for the structural study) and (Pb1.330.66Mn0.01)Σ2.00(Ta0.87Nb0.72Sn4+0.18Fe3+0.11W0.08Ti0.04)Σ2.00O6[□0.80(OH)0.10O0.10]Σ1.00 (average including additional fragments). The mineral is cubic, space group Fd$\overline 3 $m. The unit-cell parameters refined from powder X-ray diffraction data are a = 10.575(2) Å and V = 1182.6(8) Å3, which are in accord with those obtained previously from a single crystal of a = 10.571(1) Å, V = 1181.3(2) Å3 and Z = 8. The mineral description and its name have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA2015-007a).

Type
Article
Copyright
Copyright © Mineralogical Society of Great Britain and Ireland 2018 

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Footnotes

Associate Editor: Anthony Kampf

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