Vitusite — An Apatite Derivative Structure

Adrian A. Finch1, 2 and James G. Fletcher1
1 Department of Chemistry, University of Aberdeen, Meston Walk, Old Aberdeen, AB9 2UE, U.K.
2 Department of Geology and Geophysics, University of Edinburgh, West Mains Road, Edinburgh, EH9 3JW, U.K.

Abstract: The uncommon sodium rare-earth phosphate mineral vitusite-(Ce) (Na3RE(PO4)2) can be considered as the extreme product of sodium and rare-earth substitution in the apatite structure. Lesser amounts of substitution provide sodium and rare-earth-bearing apatites up to about 80 mol.% exchange; beyond this point vitusite is the stable phase. The structure of vitusite, determined previously from a synthetic analogue, can also be considered as a derivative from apatite, but with cations exchanged on sites normally occupied by anions. Vitusite can therefore be considered as a sodium- and rare-earth-rich apatite end-member, with a distinct, but apatite-derived, structure, formed in highly persodic and high rare-earth environments. From an examination of the literature on diffusion in apatite, vitusite in principle could be formed from apatite sensu stricto by subsolidus diffusion in response to late-stage Na- and RE-rich hydrothermal fluids.

Keywords: vitusite • apatite • Ilímaussaq • Gardar • South Greenland

Mineralogical Magazine; June 1992 v. 56; no. 383; p. 235-239; DOI: 10.1180/minmag.1992.056.383.10
© 1992, The Mineralogical Society
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