Comment on "a study of the phosphate mineral kapundaite NaCa(Fe 3+)4(PO4)4(OH)3 5(H2O) using SEM/EDX and vibrational spectroscopic methods" by Frost et al. (2014)

Abstract

The article presents comments on 'A study of the phosphate mineral kapundaite' using SEM/EDX and vibrational spectroscopic methods. Because kapundaite and wardite not only have a different structure but also a different chemistry, it is impossible for them to form a solid solution series, and they do not fall within the same crystal-chemical group of minerals. They present spectroscopic data for crystals whose provenance, quantitative composition and phase identity are all uncertain. In their conclusions, they claim to 'study aspects of the molecular structure' of a mineral which is already known to have an extended layer structure and is not composed at all of discrete molecules: yet another conceptual error.