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Tristramite, a new calcium uranium phosphate of the rhabdophane group

Published online by Cambridge University Press:  05 July 2018

D. Atkin ,
I. R. Basham  and
J. F. W. Bowles
D. Atkin
Affiliation:
Geochemistry and Petrology Division, Institute of Geological Sciences, 64 Gray’s Inn Road, London WC1X 8NG
I. R. Basham
Affiliation:
Geochemistry and Petrology Division, Institute of Geological Sciences, 64 Gray’s Inn Road, London WC1X 8NG
J. F. W. Bowles
Affiliation:
Geochemistry and Petrology Division, Institute of Geological Sciences, 64 Gray’s Inn Road, London WC1X 8NG
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Abstract

Tristramite, a new mineral of the rhabdophane group, has the composition (Ca0.54U4+0.29Fe3+0.17)Σ1.00 [(PO4)0.79(SO4)0.12(CO3)0.07]Σ0.98·1.77H2O. It occurs as a late-stage replacement or matrix to brecciated uraninite (var. pitchblende) associated with sulphides in hydrothermal veins related to Hercynian granites in south-west England. It is hexagonal, space group P6222, with a 6.913 ± 0.003 Å and c 6.422 ± 0.006 Å. The strongest lines of the indexed powder pattern are 2.99 (100), 2.83 (100), 2.14 (50), 1.850 (50), 5.99 (40), 4.37 (40), 3.46 (30). For comparison, new indexed powder data for rhabdophane from Fowey Consols, Cornwall, are included. The mineral is pale yellow to greenish yellow, uniaxial positive with ω 1.644 and ε 1.664, and does not fluoresce in either short-or long-wave ultraviolet light. The habit is acicular or fibrous and no cleavage has been observed. Density (g/cm3) 3.8–4.2 (meas.), 4.18 (calc.).

Type
Research Article
Information
Mineralogical Magazine , Volume 47 , Issue 344 , September 1983 , pp. 393 - 396
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1984

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