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The chemistry and structure of redledgeite

Published online by Cambridge University Press:  05 July 2018

B. M. Gatehouse ,
G. C. Jones ,
A. Pring  and
R. F. Symes
B. M. Gatehouse
Affiliation:
Department of Chemistry, Monash University, Clayton, Vic. 3168, Australia
G. C. Jones
Affiliation:
Department of Mineralogy, British Museum (Natural History), Cromwell Road, London, SW7 5BD, England
A. Pring
Affiliation:
South Australian Museum, North Terrace, Adelaide, SA 5000, Australia
R. F. Symes
Affiliation:
Department of Mineralogy, British Museum (Natural History), Cromwell Road, London, SW7 5BD, England
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Abstract

Two distinct habits of redledgeite are described: small black bipyramidal crystals and yellow-green fibres. The mineral is a Ba-Cr-Ti oxide rather than a Mg-Cr-Ti oxide as previously supposed. Electron microprobe analysis gave Ba1.10(Cr1.82Ti5.95 Fe0.10V0.08)Σ7.95O16 and Ba1.27(Cr2.48Ti5.49Fe0.02)Σ7.99 O16 for the black and yellow-green forms respectively. The mineral is a monoclinic hollandite-type phase, space group I2/m, with a = 10.129(2); b = 2.959(1); c = 10.135(2) Å; β = 90.05(11)° and Z = 1; calculated density for the black form is 4.413 g cm−3. The crystal structure was refined to R 6.3%, Rw 7.4% using 1017 reflections with F > 3σ(F) from a set of 1062 unique reflections. Electron diffraction studies revealed weak superlattice reflections, with a period of 2.24b due to tunnel cation ordering.

Keywords

redledgeitecrystal chemistryhollandite-type structureRed Ledge gold mineCalifornia
Type
Crystal structure studies
Information
Mineralogical Magazine , Volume 50 , Issue 358 , December 1986 , pp. 709 - 715
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1986

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