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X-band electron paramagnetic resonance (EPR) spectra of gamma-irradiated crystals of carbonatebearing fluorapatite from the Levant mine, Cornwall, England, revealed the presence of two previously characterized centers (i.e., an O −  defect and an O − ⃞ F  defect, where ⃞ F  represents a vacancy at the F site), a CO 2  −  radical, and a new oxygen-associated hole-like center in the anion column. The O − ⃞ F  center in carbonate-bearing fluorapatite is stable at room temperature, whereas in carbonate-free fluorapatite the stability of this radical is shifted to lower temperatures (&lt;225 K). The CO 2  −  radical herewith first reported in carbonate-bearing fluorapatite is characterized by an axial symmetry at room temperature but a weakly orthorhombic symmetry at 77 K, similar to its counterpart in carbonate-bearing hydroxylapatite. This CO 2  −  radical most likely formed from Type A carbonate ions by the loss of an O atom and trapping of an electron during gamma irradiation. The single-crystal EPR spectra of the new holelike center are characterized by the absence of any hyperfine interactions and a strongly orthorhombic symmetry. The spin Hamiltonian parameters of this new center suggest a structural model involving the trapping of a hole by a substitutional oxygen ion sandwiched between two fluorine ion vacancies in the anion column and strongly disturbed by vacancies at the neighboring Ca 2  and O 3  sites, suggesting a complex substitution of the type: □ F O 2- □ F  + □ Ca2  + CO 3  2-  → F-F-F-+ Ca 2+  + PO 4  3- .

american mineralogist

Electron paramagnetic resonance spectroscopic study of carbonate-bearing fluorapatite: New defect centers and constraints on the incorporation of carbonate ions in apatites