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Delhayelite, a new silicate from the Belgian Congo

Published online by Cambridge University Press:  14 March 2018

TH. G. Sahama
Affiliation:
Institute of Geology, University of Helsinki, Finland
Kai Hytönen
Affiliation:
Institute of Geology, University of Helsinki, Finland

Summary

The complex kalsilite-bearing melilite-nephelinite from Mt. Shaheru in the Belgian Congo with götzenite, combeite, and kirschsteinite contains yet another new silicate for which the name delhayelite is proposed.

Delhayelite is orthorhombic with a 6·53, b 24·65, c 7·04 Å. Possible space-groups Pmn21 and Pmmn. Weak super-cell with doubled a-axis. Distinct cleavage parallel to (010). Birefringence weak. αβγ = 1·532. 2Vα = 83°. Optical orientation: a = α, b = γ, c = β. Sp. gr. 2·60. Chemical composition corresponds to the tentative formula (Na,K)4Ca5Al6Si32O80.18H2O.3(Na2,K2)(Cl2,F2,SO4).

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1959

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References

Gard, (J. A.) and Taylor, (H. F. W.), 1957. Min. Mat., vol. 31, p. 611.Google Scholar
Mounttain, (E. D.), 1957 Ibid., vol. 31, p. 607.Google Scholar
Saihama, (Tg. G.) and Hytönen, (Kai), 1957a. Ibid., vol. 31, p. 503.Google Scholar
Saihama, (Tg. G.) and Hytönen, (Kai) 1957b. Ibid., vol. 31, p. 698.Google Scholar
Saihama, (Tg. G.) and Meyer, (A.), 1958. Exploration du Pare National Albert, Mission d'études vuleanologiques, Fuse. 2.Google Scholar