Banded manganiferous sediment from the Mid-Atlantic Ridge is paramagnetic at 20 °C and possibly has a Curie point at about −150 °C. Heating of the sediment in the range 520–560 °C prior to measuring probably results in the formation of a gradually changing ferrimagnetic spinel phase with a Curie point of 135 °C, which increases up to 180 °C. Heating to higher temperatures only results in a further increase in the relative abundance of the stable phase.

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