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Nancyrossite, FeGeO6H5, a new hydroxyperovskite

Part of: Ed Grew at 80: The Testimony of the Minerals

Published online by Cambridge University Press:  18 February 2025

Mark D. Welch Open the ORCID record for Mark D. Welch [Opens in a new window] ,
Jens Najorka ,
Annette K. Kleppe ,
Anthony R. Kampf Open the ORCID record for Anthony R. Kampf [Opens in a new window]  and
John Spratt
Mark D. Welch*
Affiliation:
Natural History Museum, London, SW7 5BD, UK
Jens Najorka
Affiliation:
Natural History Museum, London, SW7 5BD, UK
Annette K. Kleppe
Affiliation:
Diamond Light Source Ltd, Harwell Science and Innovation Campus, Didcot, OX11 0DE, UK;
Anthony R. Kampf
Affiliation:
Mineral Sciences Department, Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, CA, USA
John Spratt
Affiliation:
Natural History Museum, London, SW7 5BD, UK
*
Corresponding author: Mark Welch; Email: m.welch@nhm.ac.uk
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Abstract

Nancyrossite, ideally FeGeO6H5, is a new hydroxyperovskite from Tsumeb. It probably formed by the oxidation and partial dehydrogenation of stottite, FeGe(OH)6, with which it is associated intimately. The structure of nancyrossite has been determined in tetragonal space group P42/n: a = 7.37382(12) Å, c = 7.29704(19) Å, V = 396.764(16) Å3, Z = 4, R1(all) = 0.034, wR2(all) = 0.051 and GoF = 1.057. Empirical formulae of two crystals have almost end-member compositions, Fe3+1.01Zn0.03Ge0.98O6H5 and Fe3+1.01Zn0.04Ge0.98O6H5. Structure determination indicates that 88% of the Fe is ferric. The chemical formula proposed here for nancyrossite recognises that although H atoms form OH groups, writing the formula as FeGeO(OH)5 implies that one of the six oxygen atoms is very underbonded, with a bond-valence sum of only ∼1.2 valence units. As such, H in nancyrossite may have novel crystal chemistry. For example, the five H atoms may be distributed dynamically over the six O atoms, a phenomenon that would be averaged by X-ray diffraction, and so go undetected. Nancyrossite is the Ge-analogue of jeanbandyite. By analogy with nancyrossite, we propose revision of the ideal formula of jeanbandyite from FeSnO(OH)5 (Welch and Kampf, 2017) to FeSnO6H5.

Keywords

new mineralTsumebNamibiahydroxyperovskitesingle crystal X-ray diffractionRaman spectroscopy

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Type
Article
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Mineralogical Magazine , First View , pp. 1 - 8
Copyright
© The Author(s), 2025. Published by Cambridge University Press on behalf of The Mineralogical Society of the United Kingdom and Ireland.

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Footnotes

Guest Editor: Robert F. Martin

This paper is part of a collection in tribute to the work of Edward Grew at 80

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