Infrared Absorption Spectrum of α-Moganite from First-Principles

α-Moganite is a polymorph of silicon dioxide that, together with α-quartz, comprises the inorganic component of flint/chert─a material of overwhelming importance in archeology, anthropology, and paleontology. Whereas α-quartz has been studied extensively, both theoretically and experimentally, α-moganite has received considerably less attention, possibly owing to an absence of pure-phase material. In this study, we address this gap by providing a detailed first-principles analysis of the infrared (IR) absorption spectrum of α-moganite and its relation to the underlying structure. We find that the 4-membered rings of silicon and oxygen atoms, that do not appear in α-quartz, constitute a fundamental structural motif of this mineral. This distinctive arrangement results in moganite-specific fingerprints in the IR spectrum of flint/chert. This opens the door to evaluation and quantification of α-moganite content in archeological samples, providing insights into flint/chert raw material preferences and stone tool production by hominins.