Raman and infrared spectroscopic study of synthetic ungemachite, K3Na8Fe(SO4)6(NO3)2·6H2O

Iron is an important element usually found in atmospheric particulate matter, and its occurrence can be attributed to both natural and anthropogenic sources. It is an accepted fact that the atmospheric particles interact with water and other atmospheric components, therefore dissolution–crystallization processes can be expected. In this work, considering specially that low pH values are characteristic of aerosol solutions, we postulate that the rare mineral ungemachite, K3Na8Fe(SO4)6(NO3)2·6H2O can crystallize in atmosphere. The Raman and infrared spectra of synthetic ungemachite are presented and the band assignments are proposed and discussed. This is the first time that a synthetic method for ungemachite is reported.

► We found that ungemachite crystallizes from acidic aqueous solution at 20 °C.
► The Raman and IR spectra of synthetic ungemachite were recorded and bands assigned.
► The atmospheric formation of ungemachite is postulated.