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Heyite and brackebuschite compared

Published online by Cambridge University Press:  05 July 2018

R. F. Symes  and
S. A. Williams
R. F. Symes
Affiliation:
British Museum (Natural History), Cromwell Road, London, S.W. 7
S. A. Williams
Affiliation:
British Museum (Natural History), Cromwell Road, London, S.W. 7
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Summary

Heyite (see preceding paper) is so strikingly similar to brackebuschite that a close comparison of the two species seemed advisable. Topotype brackebuschite (B.M. 55819) was used for this purpose.

Brackebuschite is a vanadate of lead, manganese, and iron, heyite a vanadate of lead and iron. Both species are monoclinic with diffraction symmetry P21 or P21/m. The X-ray cells are remarkably close: a = 8·810, 8·910; b = 6·155, 6·017; c = 7·651, 7·734; β = 111° 30′, 111° 53′ (brackebuschite first). As might be expected, powder patterns are strikingly close as well.

Other than the similarities noted above, the minerals differ so fundamentally that they cannot be the same—they are valid and distinct species. Optic orientations show α: [001] 20° (in acute β) for brackebuschite, 36° (in obtuse β) for heyite. Indices are (brackebuschite first): α 2·28, 2·185; β 2·38, 2·219; γ 2·49, 2·266 for the sodium D line.

Chemical differences are irreconcilable and reaffirm brackebuschite as Pb2(Mn,Fe,Zn)(VO4)2.H2O while heyite is Pb5Fe2(VO4)2O4.

Type
Research Article
Information
Mineralogical Magazine , Volume 39 , Issue 301 , March 1973 , pp. 69 - 73
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1973

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References

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