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Johninnesite, a arsenosilicate from new sodium manganese the Kombat Mine, Namibia

Published online by Cambridge University Press:  05 July 2018

Pete J. Dunn
Affiliation:
Department of Mineral Sciences, Smithsonian Institution, Washington, DC 20560, USA
Donald R. Peacor
Affiliation:
Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan 48109, USA
Shu-Chun Su
Affiliation:
Department of Geological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA
Joseph A. Nelen
Affiliation:
Department of Mineral Sciences, Smithsonian Institution, Washington, DC 20560, USA
Oleg von Knorring
Affiliation:
21 Churchwood Avenue, Leeds LS16 5LF, England

Abstract

Johninnesite, ideally Na2Mg4Mn12As5+2 Si12043(OH)6,, is triclinic, P1 or P1̄, with a = 10.44(2), b = 11.064(6), c = 9.62(1) Å, α = 107.43(7), β = 82.7(1), γ = 111.6(1)°, V = 894(2) Å3, and Z = 1. It occurs as yellow-brown fibrous aggregates, associated with rhodonite, kentrolite, and richterite, from the Kombat Mine in Namibia. Johninnesite has cleavages on {100} and {010}, density of 3.48 (meas.), 3.51 (calc.) g/cm3. It is biaxial negative, with 2Vx = 41.9°, α = 1.6742(4), β = 1.6968(3), γ = 1.6999(3); dispersion r > υ, distinct.

Type
Silicate mineralogy
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1986

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Footnotes

*

Permanent address: Institute of Geology, Chinese Academy of Sciences, Beijing, People's Republic of China.

References

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