A Grystal-Ghemical Study of Synthetic Magnesiohastingsite

摘要: Mcissbauer and infrared spectra of synthetic magnesiohastingsite (Mh), NaCa2Mg4Fea+SisAlzOzz (OH)2, indicate that, except at high values oflo,, Fe occurs both as Fe2+ Fe3+ contrary to the ideal formula. The amount produced is a function oxygen fugacity synthesis. Oxidation reduction may be carried out reversibly under hydrothermal conditions relatively fast rates. Apparently this does not involve gain or loss O(3)-H hydroxyls case ofFe2+ bearing sodic amphiboles. Octahedrally coordinated cations are significantly ordered among M(1), M(2), M(3) sites in agreement with recent crystal-structure determinations. distribution scheme dependent on Fer+ Fea+ present. Refractive indices (c = 1.642-1.657 t :1.653-1.672),color, unit-cell parameters (a:9.928-9.933 A; b: 18.01518.029 c : 5.282-5.257 A;9 105.43-105.46o) also reflect lo, Physical properties agree well sample natural Mh similar U-1236 Larsen (1942). experimental data suggest mechanism produce Fez+ which involves an excess two protons (and/or anionic defects low lo,) per unit