Infrared Study of the Hydroxyl Bands in Clinoamphiboles

• Published in: Science (American Association for the Advancement of Science) 1966-08, Vol.153 (3738), p.890-892
• Main Authors: Burns, Roger G., Roger G. J. Strens
• Format: Article
• Language: English
• Subjects: Amphiboles; Electrons; Hydroxyls; Ions; Minerals; Ratios; Soil water; Spectral bands
• ISSN: 0036-8075; 1095-9203
• 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 Mg$^{2+}$ and Fe$^{2+}$ 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 Fe$^{2+}$-Mg$^{2+}$ amphiboles. Within any one solid-solution series, the frequencies of these peaks can be correlated with the electronegativity of ions in the M$_{1}$ and M$_{3}$ positions, and differences between series can be correlated with the size of ions in the M$_{4}$ position. The O-H vector lies approximately normal to z in the (010) plane. The distribution of Fe$^{2+}$ and Mg$^{2+}$ ions between the (M$_{1}$,M$_{3}$) and (M$_{2}$M$_{4}$) positions in the cummingtonite-grunerite series, and between the (M$_{1}$,M$_{3}$) and M$_{2}$ positions in the tremolite-ferroactinolite series, has also been estimated.