GEOC 153 |
| Rolf O. Hallberg, Department of Geology and Geochemistry, Stockholm University, S-106 91 Stockholm, Sweden and F. Grant Ferris, Department of Geology, University of Toronto, Toronto, ON M5S 3B1, Canada. |
| A new environmental scanning electron microscopic (ESEM) technique at low vacuum (5 torr) and 99% humidity, where the sample never has been exposed to high vacuum and coating of carbon or gold, has revealed a new insight into the nature of iron mineralization that develops in association with the stalked bacteria Gallionella. The stalk fibers contain minute flaky iron precipitates. The size of the crystallites is 0.1 –0.5 micron and some of them exhibit a hexagonal feature. EDAX analyses on individual crystallites give an atomic ratio between Fe and O very close to 0.67. The stoichiometric formula would thus be Fe2O3. Stoichiometry and crystallinity are in accordance with the mineral hematite. The mineralization seems to take place inside the fibers of the stalk. With time the Gallionella stalk is covered with iron oxihydroxides of different kinds that probably are controlled by inorganic processes more than by the organic chemistry of the bacteria. |
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Microbially Mediated Manganese and Iron Oxidation in the Biosphere
1:45 PM-6:20 PM, Wednesday, March 31, 2004 Marriott -- Marquis NE, Oral
Division of Geochemistry |