The magnetic susceptibility of ordered and partially disordered manganogrunerites (composition Ca0.1Mn1.9Mg1.25Fe2+3.56Fe3+0.38Si7.81O22(OH)2 and Ca0.24Mn1.57Mg2.27Fe2+2.76Fe3+0.32Si7.84O22(OH)2) has been measured between room temperature and 5 K. The influence of disordering of metal cations over the M(1,2,3) sites of the octahedral ribbon in these amphiboles is to dilute Fe2+ within the ribbon. We observe a reduction in both 𝛉p and TN as a function of both increased Mg/(Mg+Fe) and metal cation disorder, linked to a reduction in the strength of magnetic coupling between and within the one-dimensional chains of the structure.

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