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Collophane from the chalk

Published online by Cambridge University Press:  14 March 2018

George Brown  and
C. D. Ollier
George Brown
Affiliation:
Pedology Department, Rothamsted Experimental Station, Harpenden
C. D. Ollier
Affiliation:
Pedology Department, Rothamsted Experimental Station, Harpenden
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Summary

Sixteen samples of Middle and Upper Chalk from the Chilterns yielded what appear to be fragments of fish scales, spines, and bones, which consist of collophane. X-ray examination by the powder method shows that the material has an apatite-type structure with cell dimensions close to those previously reported for francolite. Examination of single grains shows that the optical anisotropy is due to preferred orientation of the c-axes of the crystallites and this direction corresponds to the faster vibration direction. Such grains are found to be pseudouniaxial negative. Preferred orientation could not be detected in isotropic grains.

Type
Research Article
Information
Mineralogical magazine and journal of the Mineralogical Society , Volume 31 , Issue 235 , December 1956 , pp. 339 - 343
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1956

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References

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