Infrared Study of the Hydroxyl Bands in Clinoamphiboles

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Science  19 Aug 1966:
Vol. 153, Issue 3738, pp. 890-892
DOI: 10.1126/science.153.3738.890


Sharp single peaks in the fundamental and first-overtone bands of the O-H stretching vibration in pure Mg2+ and Fe2+ amphiboles split into a maximum of four sharp peaks, corresponding to hydroxyl groups linked to 3 Fe, 2 Fe + Mg, 2 Mg + Fe, and 3 Mg, in mixed Fe2+-Mg2+ amphiboles. Within any one solid-solution series, the frequencies of these peaks can be correlated with the electronegativity of ions in the Ml and M3 positions, and differences between series can be correlated with the size of ions in the M4 position. The O-H vector lies approximately normal to z in the (010) plane. The distribution of Fe2+ and Mg2+ ions between the (M1,M3) and (M2M4) positions in the cummingtonite-grunerite series, and between the (M1,M3) and M2 positions in the tremolite-ferroactinolite series, has also been estimated.