Evidence for spin-pairing transitions in iron minerals

The existence of low-spin Fe2+ in pyrite formed the basis of an early estimate that spin-pairing of Fe2+ would occur in olivine at a depth in the Mantle of 

Shock-wave experiments causing phase changes in wiistite, Fe094O, and Fe203 have also produced controversial evidence for spin-pairing transitions in iron cations (Jeanloz and Ahrens, 1980 Jackson and Ringwood, 1981 Goto et al., 1982 Syono etal., 1984). 

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