Optical Spectra and Color Nature of Lithium Amphiboles

S.I. Konovalenko a*, A.I. Bakhtin b**, A.G. Nikolaev b***

a National Research Тomsk State University, Тomsk, 634050 Russia

b Kazan Federal University, Kazan, 420008 Russia

E-mail: *konov@ggf.tsu.ru, **Anatoly.Bakhtin@kpfu.ru, ***anatolij-nikolaev@yandex.ru

Received December 18, 2015

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Abstract

Optical absorption spectra of two lithium amphiboles of the pedrisite group from rare-metal pegmatites of the Sangilen rare-metal province in the southeastern part of Tyva have been studied. One of them – a limit magnesian fluoro-sodium pedrisite of yellow-green color – was taken from the rocks hosting pegmatites, and another one – fluoro-sodium ferro-pedrisite of violet-blue color – was taken from pegmatites as such. It has been demonstrated that the color of the yellow-green mineral is associated with absorption bands of Cr3+ ions in the octahedral coordination. Absorption bands of Cr3+ ions in the spectrum of fluoro-sodium pedrisite are formed by a transmission window in the yellow-green region of the spectrum. Therefore, the color of this sample is yellow-green. The color of violet-blue pedrisite is defined by intensive absorption bands of charge transfer Fe2+ → Fe3+ 550, 680 nm. Very strong absorption bands of 550 and 680 nm are formed by a transmission window in the violet-blue region of the spectrum. Thus, the color of ferro-pedrisite is violet-blue.

Keywords: optical spectra, fluoro-sodium pedrisite, fluoro-sodium ferro-pedrisite, color nature

Figure captions

Fig. 1. Absorption spectrum of violet-blue pedrisite in the polarized light: 1 – E || C; 2 – E ^ C.

Fig. 2. Absorption spectrum of yellow-green pedrisite.

References

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For citation: Konovalenko S.I., Bakhtin A.I., Nikolaev A.G. Optical spectra and color nature of lithium amphiboles. Uchenye Zapiski Kazanskogo Universiteta. Seriya Estestvennye Nauki, 2016, vol. 158, no. 1, pp. 94–100. (In Russian)


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