Precipitation of iron minerals by a natural microbial consortium

A microbial biofilm consortium enriched from Shield surface water is able to mediate geochemical cycling of iron within a biofilm. Iron can be leached from Fe(II) containing minerals such as magnetite, biotite and ilmenite to generate a colloidal Fe(III) suspension. The Fe(III) can then be reduced back to Fe(II) by iron-reducing bacteria that utilize it as an electron acceptor. On precipitation, different iron compounds are formed depending on the ratio of iron to carbon in the media and upon the local environment. Mossbauer and X-ray diffraction spectroscopy show these compounds to include ferrous hydroxide, vivianite, ferrihydrite and hematite. These minerals may then become incorporated into stratifer iron deposits such as Banded Iron Formations. Copyright (C) 1999 Elsevier Science Ltd.