FE-SEM study of microbially formed jarosites by Acidithiobacillus ferrooxidans

Morphological characterization of jarosite groups formed from Fe(III) biologically oxidized with different numbers of Acidithiobacillus ferrooxidans was conducted using FE-SEM. The higher population of A. ferrooxidans resulted in more distinct jarosite mineral shape, and stronger Raman intensities for potassium jarosite, ammoniojarosite and argentojarosite. The morphology of the jarosites might be dependent on iron-oxidizing activity of A. ferrooxidans. The technique was applied to identify jarosite compounds formed during microbially mediated dissolution of arsenopyrite by A. ferrooxidans. It is difficult to identify this jarosite compound by X-ray diffraction and Raman spectroscopy because amounts are typically low and the crystallization is poor in minerals formed by microbially mediated oxidation. However, FE-SEM image provided helpful information for identification of jarosite compounds. The results suggest that morphology would provide useful information for identification and history of jarosite minerals as geochemical samples.