Isokite, CaMg(PO(4))F(0.8)(OH)(0.2), isomorphous with titanite.
This study presents the first structural report of natural isokite (calcium magnesium phosphate fluoride), with the formula CaMg(PO(4))F(0.8)(OH)(0.2) (i.e. some substitution of OH for F), based on single-crystal X-ray diffraction data. Isokite belongs to the C2/c titanite mineral group, in which Mg is on an inversion centre and the Ca, P and F/OH atoms are on twofold axes. The structure is composed of kinked chains of corner-sharing MgO(4)F(2) octahedra that are crosslinked by isolated PO(4) tetrahedra, forming a three-dimensional polyhedral network. The Ca(2+) cations occupy the interstitial sites coordinated by six O atoms and one F anion.
Yang
Hexiong
H
Department of Geosciences, University of Arizona, 1040 East 4th Street, Tucson, AZ 85721-0077, USA. hyang@u.arizona.edu
Zwick
Justin
J
Downs
Robert T
RT
Costin
Gelu
G