Abstract

Polarized absorption spectra are reported of Cr-bearing tourmaline from Kaavi, Finland, two black tourmalines from Villeneuve, Quebec, and Como, Italy, and buergerite from San Luis Potosi, Mexico. Spectra of Cr-bearing tourmaline exhibit two strong absorption bands at 17000 cm (super -1) , characteristic of Cr (super 3+) , energy of the former band indicating that Cr (super 3+) is located in a "loose site' in the octahedral sites in the spiral chain. Spectra of black tourmalines consist of bands marking transitions within Fe (super 2+) and Fe (super 3+) ions; Mn (super 3+) may also be present in black tourmalines. Buergerite spectra show bands due to Fe (super 2+) in near infrared and red regions, but most features in the visible are swamped by charge-transfer bands. Fe is located in Al (super 3+) sites in spiral chains of black tourmalines, but mainly in "brucite units' of buergerite.

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