ABSTRACT

In the calcium-rich pyroxenes Fe²⁺ ion in the M1 positions gives rise to the inner Mössbauer doublet, and Fe²⁺ in M2 to the outer doublet. The Fe²⁺-Mg order over the M1 and M2 positions was found unexpectedly weak, being close to the complete disorder at about 1, 200°C. A four-line spectrum was observed in Di₅₀Hd₅₀ prepared by usual sintering technique at 1, 150°C. This may be due to the local disorder of Fe²⁺ and Ca. The disordered configuration seems to be metastable, and the reaction towards the ordered structure to be extremely sluggish.