Abstract
Infrared spectra of twenty-one manganoan alkali-calcic amphiboles from manganese ore deposits in Japan and India were examined. Hydroxyl stretching bands can be divided into two regions: H-bands (3750–3685 cm−1) and L-bands (3685–3600 cm−1). The H-bands’ upward frequency shift is due to the electric field arising from alkali ions in the A site, and the intensities of the H-bands are proportional to the number of alkali ions in the A site, so that the A site occupancy for each samples has been estimated by the areal ratio of these H- to L-bands. The higher frequency H-band near 3724 cm−1 is ascribed to K ions in the A site, and the lower frequency band near 3700 cm−1 to Na ions. Frequencies and features of the medium strong bands in the range of 800–740 cm−1 are sensitive not only to the A site’s alkali ions, but also to the kinds and amounts of the M4 site cations.
