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Bahianite, Sb3Al5O14(OH)2, a new species

Published online by Cambridge University Press:  05 July 2018

Paul B. Moore
Affiliation:
Department of the Geophysical Sciences, The University of Chicago, Chicago, Illinois 60637, U.S.A.
Carlos do Prado Barbosa
Affiliation:
Praca N.S. da Glorida 135-207, Rio de Janeiro 20000, Brazil
Richard V. Gaines
Affiliation:
Hoffecker Road, Pottstown, Pennsylvania 19464, U.S.A.

Summary

Bahianite, Sb3Al5O14(OH)2-Sb3Al5(Al, Be, Si)<2O16, monoclinic, a 9·406(6), b 11·541(8), c 4·410(3) Å, β 90·94(3)°, Z = 2, space group C2/m, is a new species from the Paramirim region, south central Bahia state, Brazil. It occurs as water-worn pebbles (‘favas’) with quartz, andalusite, kyanite, diaspore, eskolaite, cassiterite, etc. Colour tan to cream, crystals in vugs colourless, tan or pale violet. Specific gravity ranges from 4·89 to 5·46 (5·26 g cm−3 for Sb3Al5O14(OH)2); hardness 9, cleavage {100} perfect, lustre adamantine, biaxial (−), 2V large, α = 1·81, β = 1·87, γ = 1·92, dispersion r > v.

The crystal structure represents a new type and is based on hexagonal close-packed oxygens. It is related to the structure of simpsonite Ta3Al14O13(OH).

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1978

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References

Moore, (P. B.) and Araki, (T.), 1976. Neues Jb. Mineral., Abh. 126, 113.Google Scholar