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Bakterie magnetotaktyczne i ich minerały

Sawłowicz Z.

Przegląd Geologiczny

2016

Vol. 64, nr 5

328--337

Magnetotactic bacteria (MTB) produce magnetic minerals, magnetite (Fe3O4) and greigite (Fe3S4) in their cells. These magnetosome crystals form chains which allow bacterial cells to align with the Earth magnetic field. Magneto-aerotaxis allows bacteria to find optimal growth conditions in the water column. MTB species and their habitats are described, along with the description of minerals and the origin of magnetosomes. Fossil MTB are used to solve different geological problems they especially influence rock magnetism. Cultured magnetotactic bacteria and their nanominerals find more and more applications in many disciplines.

Magnetic monitoring of thermal alteration for natural pyrite and greigite

Tudryn A., Tucholka P.

Acta Geophysica Polonica

2004

Vol. 52, nr 4

509-520

Pure pyrite and greigite and pyrite/greigite mixtures were submitted to Curie balance experiments. The magnetic monitoring of the alteration of pyrite with temperature shows that at about 500°C magnetite always appears and can alter after-wards to hematite depending on the experimental conditions. Therefore, an increase of magnetisation due to the magnetite suggests the presence of pyrite in the studied samples. Samples with a pyrite/greigite mixture show minimum magnetisation during heating at 400°C, and its subsequent immediate increase. The increase of magnetisation is much higher in samples dominated by pyrite than in samples dominated by greigite. This behaviour can allow identification of pyrite in a pyrite /greigite mixture. Alteration with temperature of pyrite and greigite, which implies the appearance of magnetic minerals, can be used in magnetic and environmental studies.