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Iron ores and mineral spring water from Gumma Iron Mine were examined mainly by TEM. Biomineralization was found on diatom and bacteria in the spring water, and also on living moss. Aggregates of cyanobacteria-like fossils were found in some iron ore which is composed of goethite and jarosite. They were examined by EPMA and TEM (lattice imaging). The formation mechanism of iron ore was discussed and biogenic contribution to the ore formation was suggested.
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Akai et al. (1996) studied this question.
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