Montes-Hernandez et al. [5] recently reported results of a study of the decarbonation of fine-grained synthetic bastnasite-(Ce) precipitates involving the oxidation of Ce(III) to Ce(IV) and the formation of ceria (CeO2 and CeO2-x with oxygen vacancies) nano-particles. The purpose of their study was to show that oxidation of Ce(III) to Ce(IV) occurs spontaneously during heating of bastnasite-(Ce) in air, a vacuum, N-2 or Ar gas. However, their interpretation of the formation of CeO2 is not supported by the findings of Gysi and Williams Jones [3], who showed that natural bastnasite-(Ce) decomposes to form rare earth element (REE) oxyfluorides (REEOF). The latter was documented using differential scanning calorimetric (DSC) and thermogravimetric (TGA) experiments under a deoxygenated N-2 atmosphere. In their experiments, Gysi and Williams Jones [3] found no evidence for the oxidation of Ce(III) to Ce(IV). This raises the question of whether the experiments of Montes-Hernandez et al. [5] in a N-2 atmosphere (and by extension in an Ar atmosphere) were compromised because of contamination by O-2 and that, as a result, they reached the erroneous conclusion that Ce(III) oxidizes spontaneously to Ce(IV) during heating of bastnasite-(Ce) under these conditions. In order to explain the disagreement between their findings and those of Gysi and Williams Jones [3], Montes-Hernandez et al. [5], proposed that the X-ray diffraction data of the former study were incorrectly interpreted. Here, we provide further evidence that the natural bastnasite-(Ce) employed in the study by Gysi and Williams Jones [3] decomposed to form REE oxyfluorides (i.e., CeOF, LaOF, PrOF and NdOF) and not CeO2, and supply explanations for why Montes-Hernandez et al. [5] erroneously concluded that CeO2 is produced during decomposition of this mineral under N-2 and Ar atmospheres. In so doing, we hope to provide new insights into the decomposition of bastnasite-(Ce) that will help guide future studies of this fascinating mineral. We also show how the thermodynamic data of Gysi and Williams Jones [3] can be used to evaluate the conditions at which bastnasite-(Ce) is stable in hydrothermal fluids. (C) 2016 Elsevier B.V. All rights reserved.