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The crystal chemistry of the apatites

Published online by Cambridge University Press:  14 March 2018

A. G. Cockbain
A. G. Cockbain*
Affiliation:
Allen Clark Research Centre, The Plessey Company Limited, Caswell, Towcester, Northamptonshire
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Summary

The compositions of more than eighty synthetic members of the apatite group with the general formula A10(XO4)6Z2 have been used as a basis for classifying the apatites into three groups. The ratios of the mean sizes of the ‘A’ ions to those of the ‘X’ ions for all these compositions lie between the limits of 1·89 and 4·43. A discontinuity occurs between ratios of 2·50 and 2·60 and probably another between 3·25 and 3·35, and these discontinuities provide a structural basis for the division into the three groups. The groups are named after well-known mineral species occurring in each group, i.e. the vanadinite-svabites with an A : X ratio less than 2·5, the apatite-mimetites between 2·60 and 3·25, and the pyromorphites with A : X greater than 3·25.

Type
Research Article
Information
Mineralogical magazine and journal of the Mineralogical Society , Volume 36 , Issue 281 , March 1968 , pp. 654 - 660
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1968

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